ASPECT MEDICAL SYSTEMS INC
S-1/A, 1998-07-16
ELECTROMEDICAL & ELECTROTHERAPEUTIC APPARATUS
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<PAGE>   1
 
   
     AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JULY 16, 1998
    
 
   
                                                      REGISTRATION NO. 333-57739
    
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
 
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                            ------------------------
   
                                AMENDMENT NO. 1
    
   
                                       TO
    
 
                                    FORM S-1
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933
                            ------------------------
 
                          ASPECT MEDICAL SYSTEMS, INC.
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)
                            ------------------------
 
<TABLE>
<S>                                <C>                                <C>
             DELAWARE                             3845                            04-2985553
 (STATE OR OTHER JURISDICTION OF      (PRIMARY STANDARD INDUSTRIAL             (I.R.S. EMPLOYER
  INCORPORATION OR ORGANIZATION)      CLASSIFICATION CODE NUMBER)           IDENTIFICATION NUMBER)
</TABLE>
 
                            ------------------------
 
                                TWO VISION DRIVE
                          NATICK, MASSACHUSETTS 01760
                                 (508) 653-0603
    (ADDRESS, INCLUDING ZIP CODE, AND TELEPHONE NUMBER, INCLUDING AREA CODE,
                  OF REGISTRANT'S PRINCIPAL EXECUTIVE OFFICES)
 
                            ------------------------
 
                               NASSIB G. CHAMOUN
                     PRESIDENT AND CHIEF EXECUTIVE OFFICER
                          ASPECT MEDICAL SYSTEMS, INC.
                                TWO VISION DRIVE
                          NATICK, MASSACHUSETTS 01760
                                 (508) 653-0603
               (NAME, ADDRESS, INCLUDING ZIP CODE, AND TELEPHONE
               NUMBER, INCLUDING AREA CODE, OF AGENT FOR SERVICE)
                            ------------------------
 
                                   COPIES TO:
 
<TABLE>
<S>                                                 <C>
               SUSAN W. MURLEY, ESQ.                               LESLIE E. DAVIS, ESQ.
                 HALE AND DORR LLP                            TESTA, HURWITZ & THIBEAULT, LLP
                  60 STATE STREET                                    HIGH STREET TOWER
            BOSTON, MASSACHUSETTS 02109                               125 HIGH STREET
             TELEPHONE: (617) 526-6000                          BOSTON, MASSACHUSETTS 02110
             TELECOPY: (617) 526-5000                            TELEPHONE: (617) 248-7000
                                                                 TELECOPY: (617) 248-7100
</TABLE>
 
                            ------------------------
 
    APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC:  As soon as
practicable after the effective date hereof.
 
    If any of the securities being registered on this Form are to be offered on
a delayed or continuous basis pursuant to Rule 415 under the Securities Act,
check the following box. [ ]
 
    If this Form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, check the following box and
list the Securities Act registration statement number of the earlier effective
registration statement for the same offering. [ ]
- ------------
 
    If this Form is a post-effective amendment filed pursuant to Rule 462(c)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering. [ ]
- ------------
 
    If this Form is a post-effective amendment filed pursuant to Rule 462(d)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering. [ ]
- ------------
 
   
    If delivery of the prospectus is expected to be made pursuant to Rule 434,
check the following box. [ ]
    
                            ------------------------
 
    THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR
DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL
FILE A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION
STATEMENT SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(A) OF
THE SECURITIES ACT OF 1933 OR UNTIL THE REGISTRATION STATEMENT SHALL BECOME
EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(A),
MAY DETERMINE.
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<PAGE>   2
 
                                                           SUBJECT TO COMPLETION
   
                                                                   JULY 16, 1998
    
 
   
                                3,100,000 Shares
    
 
                                      LOGO
 
                                  Common Stock
                               ------------------
 
   
     All the 3,100,000 shares of Common Stock offered hereby will be sold by
Aspect Medical Systems, Inc. ("Aspect" or the "Company"). Prior to this
offering, there has been no public market for the Common Stock of the Company.
It is presently estimated that the initial public offering price will be between
$12.00 and $14.00 per share. See "Underwriting" for the factors to be considered
in determining the initial public offering price. Application has been made for
the quotation of the Common Stock on the Nasdaq National Market under the symbol
"ASPM."
    
                               ------------------
 
        THE COMMON STOCK OFFERED HEREBY INVOLVES A HIGH DEGREE OF RISK.
                    SEE "RISK FACTORS" BEGINNING ON PAGE 5.
                               ------------------
 
  THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
 EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE SECURITIES
   AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION PASSED UPON THE
ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
                               CRIMINAL OFFENSE.
 
<TABLE>
<S>                                <C>                       <C>                       <C>
- ---------------------------------------------------------------------------------------------------------------
- ---------------------------------------------------------------------------------------------------------------
                                            PRICE                  UNDERWRITING                PROCEEDS
                                              TO                  DISCOUNTS AND                   TO
                                            PUBLIC                 COMMISSIONS                COMPANY(1)
- ---------------------------------------------------------------------------------------------------------------
Per Share........................             $                         $                         $
- ---------------------------------------------------------------------------------------------------------------
Total(2).........................             $                         $                         $
- ---------------------------------------------------------------------------------------------------------------
- ---------------------------------------------------------------------------------------------------------------
</TABLE>
 
   
(1) Before deducting expenses estimated at $850,000, payable by the Company.
    
   
(2) The Company has granted the Underwriters a 30-day option to purchase up to
    465,000 additional shares of Common Stock solely to cover over-allotments,
    if any. To the extent the option is exercised, the Underwriters will offer
    the additional shares at the Price to Public shown above. If the option is
    exercised in full, the total Price to Public, Underwriting Discounts and
    Commissions and Proceeds to Company will be $          , $          and
    $          , respectively. See "Underwriting."
    
                               ------------------
 
     The shares of Common Stock are offered by the several Underwriters, subject
to prior sale, when, as and if delivered to and accepted by them, and subject to
the right of the Underwriters to reject any order in whole or in part. It is
expected that delivery of the shares of Common Stock will be made through the
facilities of the Depository Trust Company in New York, New York, on or about
            , 1998 against payment therefor in immediately available funds.
 
BT AlexS Brown
 
                              Merrill Lynch & Co.
 
                                                              Piper Jaffray Inc.
 
               THE DATE OF THIS PROSPECTUS IS             , 1998.
 
INFORMATION CONTAINED HEREIN IS SUBJECT TO COMPLETION OR AMENDMENT. A
REGISTRATION STATEMENT RELATING TO THESE SECURITIES HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION. THESE SECURITIES MAY NOT BE SOLD NOR MAY
OFFERS TO BUY BE ACCEPTED PRIOR TO THE TIME THE REGISTRATION STATEMENT BECOMES
EFFECTIVE. THIS PROSPECTUS SHALL NOT CONSTITUTE AN OFFER TO SELL OR THE
SOLICITATION OF AN OFFER TO BUY NOR SHALL THERE BE ANY SALE OF THESE SECURITIES
IN ANY STATE IN WHICH SUCH OFFER, SOLICITATION OR SALE WOULD BE UNLAWFUL PRIOR
TO REGISTRATION OR QUALIFICATION UNDER THE SECURITIES LAWS OF ANY SUCH STATE.
<PAGE>   3
 
   
[Company Logo]
    
 
   
     Aspect has developed the only FDA-cleared, commercially available product
for use as a direct measure of the effects of anesthetics on the brain. The BIS
index is a numerical index derived from the combination of several processed EEG
variables that correlate with loss of consciousness and changes in levels of
sedation. The BIS System, which incorporates the BIS index, is comprised of the
Company's BIS monitor and single-use, disposable BIS Sensors.
    
 
   
[Photograph depicting the Company's A-2000 BIS monitor]
    
 
   
     The A-2000 BIS Monitor is a compact, portable monitor designed to
accommodate the space limitations and positioning requirements of surgical
settings. The A-2000 displays the BIS index and supporting information on a high
contrast electro-luminescent display and includes Aspect's proprietary Digital
Signal Converter.
    
 
[Photograph depicting the Company's A-2000 BIS Monitor product with BIS Sensor
affixed to model's forehead]
 
   
     The BIS Sensor provides a reliable and simple means of acquiring the EEG
signal needed to generate the BIS index. The BIS Sensor is a single-piece,
single-use disposable product for use with the A-2000, the A-1050 monitor and
the BIS Module Kit.
    
 
[Photograph depicting the Company's BIS Sensor, BIS Module Kit and Digital
Signal Converter products]
 
   
     In 1996, Aspect introduced the BIS Module Kit, which requires the use of
the BIS Sensor in order to calculate the BIS index. The BIS Module Kit is
designed to facilitate the integration of the Company's BIS index into
monitoring products marketed by third parties that enter into OEM arrangements
with the Company.
    
   
    
 
                            ------------------------
 
     CERTAIN PERSONS PARTICIPATING IN THIS OFFERING MAY ENGAGE IN TRANSACTIONS
THAT STABILIZE, MAINTAIN OR OTHERWISE AFFECT THE PRICE OF THE COMMON STOCK,
INCLUDING OVER-ALLOTMENT, STABILIZING AND SYNDICATE SHORT-COVERING TRANSACTIONS
IN SUCH SECURITIES, AND THE IMPOSITION OF A PENALTY BID. FOR A DESCRIPTION OF
THESE ACTIVITIES, SEE "UNDERWRITING."
                            ------------------------
 
   
     BIS, Bispectral Index, A-1050, A-2000 and Zipprep are trademarks of Aspect
Medical Systems, Inc. Aspect is a registered trademark licensed on a
non-exclusive basis to the Company. All other trademarks or trade names referred
to in this Prospectus are the property of their respective owners.
    
                                        2
<PAGE>   4
 
                               PROSPECTUS SUMMARY
 
     The following summary is qualified in its entirety by the more detailed
information and the Financial Statements and Notes thereto appearing elsewhere
in this Prospectus. This Prospectus contains forward-looking statements that
involve risks and uncertainties. The Company's actual results could differ
significantly from the results discussed in the forward-looking statements.
Factors that might cause such a difference include, but are not limited to,
those discussed in "Risk Factors."
 
                                  THE COMPANY
 
   
     Aspect develops, manufactures and markets anesthesia monitoring systems
that enable anesthesia providers to assess levels of consciousness and
administer the appropriate amount of anesthetics during surgery. The BIS System
incorporates the Company's proprietary disposable BIS Sensors and the A-2000 BIS
Monitor, which was cleared for marketing by the United States Food and Drug
Administration (the "FDA") in February 1998. The BIS System is based on Aspect's
patented core technology, the Bispectral Index (the "BIS index"), which is the
only FDA-cleared, commercially available, direct measure of the effects of
anesthetics on the brain. The BIS System was developed over a ten-year period
and is the subject of eight issued and five pending United States patents.
Aspect markets the BIS System through a direct sales organization in the United
States. As of July 4, 1998, more than 880 BIS monitors have been sold to
approximately 140 sites in the United States, and the Company believes that over
150,000 patients have been monitored using the BIS index during surgery.
    
 
   
     Each year, more than 29 million patients in the United States and 42
million patients in Europe and Japan receive anesthesia in surgical procedures.
Of these 71 million patients, more than 60% receive general anesthesia or deep
sedation monitored by an anesthesia provider. Historically, anesthesia providers
have had no direct means of assessing levels of consciousness during surgery and
have generally relied on recommended drug dosages and indirect indicators of
consciousness, including blood pressure and heart rate. Changes in these
indirect measures, however, are not reliable indicators of changes in a
patient's levels of consciousness. Using existing monitoring devices, anesthesia
providers are sometimes unable to detect surgical awareness, or the
unintentional regaining of consciousness during surgery. The Company believes
the desire to prevent surgical awareness, as well as the difficulty of
accounting for variability in patient tolerances to anesthetic drugs, leads
anesthesia providers to administer more anesthetic than is required by many of
their patients. Overmedication results in increased drug costs, prolonged and
unpredictable wake-ups from anesthesia and prolonged recovery in the Post
Anesthesia Care Unit (the "PACU"). These factors, in turn, lead to
inefficiencies in operating room (the "OR") and PACU scheduling and increased
personnel costs.
    
 
   
     Aspect's BIS index is designed to allow anesthesia providers to measure
directly the effects of anesthetics on the brain in order to assess levels of
consciousness and to administer the appropriate amount of anesthetics for
surgical procedures, while avoiding unintentional overmedication or
undermedication. The BIS index ranges from 100, indicating the patient is awake,
to zero, indicating an absence of electrical brain activity. The Company has
demonstrated in a 302-patient prospective, randomized, controlled utility trial
that BIS monitoring provides more controlled and cost-effective dosing of
anesthetic drugs, faster and more predictable recovery from anesthesia and
improved quality of recovery.
    
 
   
     Aspect's objective is to become a major multinational anesthesia monitoring
company by establishing BIS monitoring as the standard of practice in anesthesia
and sedation monitoring in the OR, in the intensive care unit and for procedures
requiring sedation outside the OR. Key elements of the Company's strategy to
accomplish its objective include: (i) a direct sales force for rapid
commercialization, (ii) clinical specialists to educate and to promote the use
of Aspect's BIS System, (iii) OEM relationships to broaden distribution
channels, (iv) technological leadership and (v) new product development.
    
 
     The Company was organized in Delaware in 1987. The Company's principal
executive offices are located at Two Vision Drive, Natick, Massachusetts 01760,
and its telephone number is (508) 653-0603.
 
                                        3
<PAGE>   5
 
                                  THE OFFERING
 
   
Common Stock offered by the Company...........   3,100,000 shares
    
 
   
Common Stock to be outstanding after the
offering......................................   14,166,974 shares(1)
    
 
Use of proceeds...............................   To fund sales and marketing,
                                                 research and development,
                                                 the sales-type lease
                                                 program, possible
                                                 acquisitions and working
                                                 capital and other corporate
                                                 purposes
 
Proposed Nasdaq National Market symbol........   ASPM
 
                         SUMMARY FINANCIAL INFORMATION
                     (IN THOUSANDS, EXCEPT PER SHARE DATA)
 
   
<TABLE>
<CAPTION>
                                       YEAR ENDED DECEMBER 31,                  SIX MONTHS ENDED
                           ------------------------------------------------   --------------------
                                                                              JUNE 28,    JULY 4,
                            1993      1994      1995      1996       1997       1997        1998
                           -------   -------   -------   -------   --------   ---------   --------
                                                                                  (UNAUDITED)
<S>                        <C>       <C>       <C>       <C>       <C>        <C>         <C>
STATEMENTS OF OPERATIONS DATA:
  Revenue................  $   155   $   852   $ 1,067   $ 1,389   $  3,068   $   1,076   $ 4,420
  Loss from operations...   (3,885)   (4,491)   (5,607)   (5,477)   (10,308)     (4,655)   (6,814)
  Net loss...............   (3,657)   (4,260)   (5,546)   (5,396)    (9,886)     (4,447)   (6,517)
  Pro forma basic and
     diluted net loss per
     share(2)............                                          $  (1.28)              $ (0.65)
  Weighted average shares
     used to compute pro
     forma net loss per
     share(2)............                                             7,707                 9,951
</TABLE>
    
 
   
<TABLE>
<CAPTION>
                                                                    JULY 4, 1998
                                                              -------------------------
                                                              ACTUAL     AS ADJUSTED(3)
                                                              -------    --------------
                                                                     (UNAUDITED)
<S>                                                           <C>        <C>
BALANCE SHEET DATA:
  Cash, cash equivalents and marketable securities..........  $10,131       $46,760
  Working capital...........................................    7,143        43,772
  Total assets..............................................   16,125        52,754
  Long-term debt............................................      682           682
  Total stockholders' equity................................    9,299        45,928
</TABLE>
    
 
- ---------------
   
(1) Based on the number of shares of Common Stock outstanding on July 16, 1998.
    Excludes an aggregate of 1,730,755 shares of Common Stock reserved for
    issuance pursuant to exercise of currently outstanding options at a weighted
    average exercise price of $4.28 per share. See "Management -- Executive
    Compensation" and Note 9 of Notes to Financial Statements.
    
(2) See Note 10 of Notes to Financial Statements.
   
(3) Adjusted to give effect to the estimated net proceeds based upon an assumed
    public offering price of $13.00 per share.
    
 
   
     Unless otherwise indicated, all information contained in this Prospectus
(i) reflects the conversion of all outstanding shares of the Company's Series
A-1, Series B-1, Series C and Series D Convertible Preferred Stock (the
"Convertible Preferred Stock") into an aggregate of 9,313,509 shares of Common
Stock at the closing of this offering and (ii) assumes no exercise of the
Underwriters' over-allotment option. The Company follows a system of fiscal
months as opposed to calendar months. Under this system, the first eleven months
of each fiscal year end on a Saturday and the last month of the fiscal year
always ends on December 31. All references to the six months ended June 28, 1997
relate to the period from January 1, 1997 to June 28, 1997, and all references
to the six months ended July 4, 1998 relate to the period from January 1, 1998
to July 4, 1998.
    
                                        4
<PAGE>   6
 
                                  RISK FACTORS
 
     In addition to the other information in this Prospectus, the following
factors should be considered carefully in evaluating an investment in the shares
of Common Stock offered by this Prospectus.
 
UNCERTAINTY OF MARKET ACCEPTANCE OF TECHNOLOGY AND PRODUCTS
 
     Commercial introduction of the Company's BIS monitor, BIS Sensor and
related products (collectively, the "BIS System") commenced in late 1996, and to
date sales of BIS Systems have been limited. The commercial success of the BIS
System will depend on its acceptance by hospitals and anesthesia providers as an
accurate, reliable and cost-effective method of monitoring the effects of
anesthetics on the brain in order to assess levels of consciousness. There can
be no assurance that anesthesia providers will modify their current practice
methods and support the BIS System as a complement to current anesthesia
monitoring. In addition, market acceptance of the BIS System will depend in part
on the Company demonstrating that the cost of a BIS System would be offset by a
reduction in costs associated with administering anesthesia, including the costs
of drugs and post-operative recovery time. Even if the Company is successful in
marketing and selling BIS monitors, there can be no assurance that customers
will continue to use such monitors or that the Company will be successful in
generating sales of BIS Sensors. Failure of the Company's BIS System to provide
an accurate and reliable measure of the effects of anesthetics on the brain in
order to assess levels of consciousness, whether because of misuse, malfunction
or otherwise, could have a material adverse effect on market acceptance of BIS
Systems. For example, cases of surgical awareness, or the unintentional
regaining of consciousness during surgery, undetected by Bispectral Index (the
"BIS index") monitoring may occur, and the resulting adverse publicity could
result in the failure of anesthesia providers and hospitals to adopt BIS
Systems, which would have a material adverse effect on the business, financial
condition and results of operations of the Company. In addition, market
acceptance of the Company's BIS System could be adversely affected by events
outside its control, including the introduction of superior competitive products
or the failure of competitive products to perform in accordance with customers'
expectations.
 
LIMITED MARKETING AND SALES EXPERIENCE
 
     The Company has only limited sales and marketing experience in the United
States and no direct sales experience outside the United States. No assurance
can be given that the Company's direct sales force and clinical specialist group
will be successful in promoting BIS Systems. The sales effort is typically
lengthy, in part because the Company generally must educate potential customers
about the clinical benefits and cost effectiveness of BIS Systems. There can be
no assurance that the Company's education or other sales strategies are properly
developed or that they will be successfully implemented. The Company is also
evaluating international and other domestic marketing and sales channels,
including contract sales organizations, distributors and marketing partners. The
Company's failure to develop and implement successfully its sales and marketing
strategy would have a material adverse effect on the Company's business,
financial condition and results of operations. See "Business -- Sales, Marketing
and Customers."
 
RELIANCE ON SINGLE PRODUCT FAMILY
 
   
     The BIS System is the Company's only product. To date, the BIS System has
not achieved widespread market acceptance and sales have been limited. The
failure of the Company to gain widespread market acceptance of BIS Systems would
have a material adverse effect on the Company's business, financial condition
and results of operations. In addition, sales of BIS Sensors are dependent upon
continued use by customers of the BIS monitors. There can be no assurance that
customers will continue to use BIS monitors or purchase BIS Sensors. Moreover,
there can be no assurance the Company will further enhance its products for use
outside of the operating room (the "OR"), including in the intensive care unit
("ICU"), for conscious sedation or for other applica-
    
                                        5
<PAGE>   7
 
tions. The Company's failure to develop its products for use outside of the OR
would have a material adverse effect on the Company's business, financial
condition and results of operations. See "-- Uncertainty of Market Acceptance of
Technology and Products" and "Management's Discussion and Analysis of Financial
Condition and Results of Operations."
 
LIMITED MANUFACTURING EXPERIENCE; MANUFACTURING EXPANSION
 
     Aspect relies on third-party manufacturers to assemble and manufacture the
components of its BIS monitors. The Company performs final assembly and testing
of the BIS monitors. The Company has historically outsourced the manufacturing
of its BIS Sensor, but in the first quarter of 1998, the Company began
manufacturing a portion of the BIS Sensors in its own manufacturing facility.
The failure of the Company or any contract manufacturer to produce enough
components or products on time, cost-effectively and in compliance with
applicable licensing or regulatory requirements, such as the Good Manufacturing
Practices ("GMPs") of the United States Food & Drug Administration (the "FDA"),
including the FDA's Quality Systems Regulations, would have a material adverse
effect on the Company's business, results of operations and financial condition.
Any termination or modification of any manufacturing arrangement with a
third-party could result in a business interruption for the Company. The Company
may require additional manufacturing capacity within the next two years. There
can be no assurance that the Company will be successful in expanding its
manufacturing facility or relocating its facility to meet demand in a timely
manner or within budget. The Company has only one manufacturing facility and any
loss of, damage to or interruption of production at its facility could have a
material adverse effect on the Company's business, financial condition and
results of operations. See "Business -- Manufacturing."
 
DEPENDENCE ON SINGLE OR LIMITED SOURCE SUPPLIERS
 
     The Company currently obtains certain key components of its BIS Systems,
including certain components used in the BIS Sensors, from single or limited
sources. The Company purchases components pursuant to purchase orders rather
than long-term supply agreements. The Company has experienced shortages and
delays in obtaining certain components of its BIS Systems in the past. There can
be no assurance that the Company will not experience similar delays or shortages
in the future. The disruption or termination of the supply of components or a
significant increase in the costs of these components from these sources could
have a material adverse effect on the Company's business, financial condition
and results of operations. Furthermore, if the Company is required to change the
manufacturer of a key component of the BIS System, the Company may be required
to verify that the new manufacturer maintains facilities and procedures that
comply with all applicable regulations and guidelines. The delays associated
with verification could delay the manufacture and sale of the Company's BIS
Systems and any delay could have a material adverse effect on the Company's
business, financial condition and results of operations. See "Business --
Manufacturing."
 
TECHNOLOGICAL RISKS
 
     The medical industry is characterized by rapid product development and
technological advances. There can be no assurance that new monitoring products,
alternative techniques for evaluating the effects of anesthesia, significant
changes in the methods of delivering anesthesia or new anesthetic agents will
not be developed that will render the Company's current or planned products
obsolete or inferior. New products or technologies used on patients or in the OR
during surgery, or electrical or mechanical interference from new or existing
products or technologies, could also adversely affect the performance of the BIS
index. The effect of technological changes on the Company's business cannot be
predicted and could have a material adverse effect on the Company's business,
financial condition and results of operations.
 
     Additional studies, sponsored in part by the Company, are ongoing to assess
the performance of the BIS index in the presence of certain anesthetics, such as
ketamine, and patient populations, such
                                        6
<PAGE>   8
 
as children, not included in the clinical development of the BIS algorithms.
There can be no assurance that the BIS technology will be effective in
monitoring these or other anesthetic agents and patient populations or when
other anesthetic techniques are used. Furthermore, there can be no assurance
that the Company will be successful in developing any product enhancements or
extensions or new products, including products for use in the ICU, for conscious
sedation or for other applications. The failure of the Company to develop
product enhancements or extensions or new products could have a material adverse
effect on the Company's business, financial condition and results of operations.
 
DEPENDENCE ON KEY PERSONNEL; NEED FOR ADDITIONAL PERSONNEL
 
     The Company's success is substantially dependent on the ability, experience
and performance of its senior management and other key personnel. The Company
needs to hire, train, retain and motivate additional personnel, particularly
sales representatives and clinical specialists who are responsible for customer
education and training and post-installation customer support. The Company
continues to experience difficulty in recruiting and retaining qualified
personnel because the pool of experienced persons is small and the Company
competes for such personnel with other companies, many of which have greater
resources than the Company. The failure of the Company to hire and retain
required personnel, including sales representatives and clinical specialists,
would have a material adverse effect on the Company's business, financial
condition and results of operations. See "Business -- Sales, Marketing and
Customers," "Business -- Employees" and "Management."
 
COMPETITION
 
   
     Although products incorporating the BIS index are currently the only
devices cleared by the FDA to measure the effects of anesthetics on the brain,
the Company expects to face substantial competition. The Company believes that
competition will initially come from companies, including patient monitoring
companies, currently marketing conventional EEG monitors utilizing standard
signal-processing techniques such as the Spectral Edge Frequency and Median
Frequency or from companies that market EEG monitors utilizing novel
signal-processing technologies, including at least two companies that are
currently conducting clinical trials on products under development.
Additionally, a number of academic researchers worldwide are studying the
potential use of other techniques to measure the effects of anesthetics,
including the use of auditory evoked potentials, heart rate variability,
pupillary reflexes and skin blood flow measurement techniques. Competitors that
develop a product that is substantially equivalent to an FDA-cleared product
developed by the Company may use the Company's product as a predicate device to
obtain more quickly FDA clearance under the 510(k) process. Accordingly, there
can be no assurance that competitors will not develop and market products that
compete with any of the Company's products in less time than it took the Company
to develop its products. Further, the Company may face substantial competition
from companies developing sensor products that compete with the Company's
proprietary BIS Sensors for use with the Company's BIS monitors. Competitors in
some jurisdictions outside the United States may enter the market without delays
caused by regulatory barriers that exist in the United States. Many of the
Company's potential competitors have substantially greater financial, marketing,
technical, manufacturing and distribution resources than those of the Company
and the Company expects to compete in areas in which the Company has limited
experience, including manufacturing, marketing and sales and customer service
and support. Competition from other companies may also force the Company to
reduce the price of its products. There can be no assurance that the Company
will be able to compete successfully or that competition, including the
development and commercialization of new products and technology, will not have
a material adverse effect on the Company's business, financial condition and
results of operations. See "Business -- Competition."
    
 
                                        7
<PAGE>   9
 
DEPENDENCE ON PATENTS, TRADEMARKS, LICENSES AND PROPRIETARY RIGHTS
 
     Aspect believes that its success depends, in part, on obtaining patent
protection for its products, defending patents once obtained, preserving its
trade secrets and operating without infringing upon patents and proprietary
rights held by third parties, both in the United States and in foreign
countries. There can be no assurance that the Company has or will develop or
obtain additional rights to products or processes that are patentable, that
patents will issue from any of the pending patent applications filed by the
Company or that claims allowed will be sufficient to protect the Company's
technology or technology that is licensed to the Company. In addition, no
assurances can be given that any patents issued to or licensed by the Company
will not be challenged, invalidated, infringed or circumvented or that the
rights granted thereunder will provide competitive advantages for the Company's
business or products. The Company may be subject to further risks as it expands
its operations in countries where intellectual property laws are not well
developed or are difficult to enforce. Legal protections of the Company's
proprietary rights may be ineffective in those countries. In such event, the
business, results of operations and financial condition of the Company could be
materially adversely affected.
 
     There has been substantial litigation regarding patent and other
intellectual property rights in the medical devices industry. The Company has in
the past been involved in patent litigation and future litigation may be
necessary to protect patents, trade secrets, copyrights or "know-how" owned by
or licensed to the Company or to defend the Company against claimed infringement
of the rights of others and to determine the scope and validity of the
proprietary rights of the Company and others. The validity and breadth of claims
covered in medical technology patents involve complex legal and factual
questions for which important legal principles are unresolved. Any intellectual
property litigation could result in substantial cost to and diversion of effort
by the Company. Adverse determinations in any litigation could subject the
Company to significant liabilities to third parties, could require the Company
to seek licenses from third parties with unfavorable terms, if at all, and could
prevent the Company from manufacturing, selling or using certain of its
products, any of which could have a material adverse effect on the Company's
business, financial condition and results of operations.
 
     The Company also relies on trade secrets and proprietary technology that it
seeks to protect, in part, through confidentiality agreements with employees,
consultants and other parties. There can be no assurance that these agreements
will not be breached, that the Company will have adequate remedies for any
breach, that others will not independently develop substantially equivalent
proprietary information or that third parties will not otherwise gain access to
the Company's trade secrets.
 
     The Company also relies upon trademarks and trade names for the development
and protection of brand loyalty and associated goodwill in connection with its
products. There can be no assurance that any registered or unregistered
trademarks or trade names owned by or licensed to the Company will not be
challenged, cancelled, infringed, circumvented, or be declared generic or
infringing of other third-party marks or provide any competitive advantage to
the Company. The Company also is a party to a license agreement with a third
party pursuant to which it has obtained the nonexclusive right to make, use
and/or sell products under the name "Aspect." The licensor of the Aspect name
markets products for use in the health care industry. There can be no assurance
that there will not be confusion in the market between the Company and such
licensor or that any such confusion would compromise the competitive advantage,
if any, the Company derives from its name. See "Business -- Patents and
Proprietary Rights."
 
HISTORY OF LOSSES; UNCERTAINTY OF PROFITABILITY
 
   
     The Company has incurred losses since inception. The Company incurred net
losses of $5.5 million, $5.4 million, $9.9 million and $6.5 million during 1995,
1996, 1997 and the six months ended July 4, 1998, respectively. The Company
expects to continue to incur operating losses
    
 
                                        8
<PAGE>   10
 
in future periods, and there can be no assurance that the Company will ever
achieve or sustain profitability. See "Management's Discussion and Analysis of
Financial Condition and Results of Operations."
 
FLUCTUATIONS IN QUARTERLY OPERATING RESULTS
 
     The Company's results of operations have varied significantly from quarter
to quarter. Quarterly operating results will depend upon several factors, many
of which are not in the Company's control, including commercial acceptance of
the Company's products, both in the United States and internationally, timing
and cancellation of customer orders, cost of product upgrades, continued use by
customers of BIS monitors and, accordingly, sales of BIS Sensors, the
introduction of new products by the Company or competitors, the mix between
pilot production of new products and full scale manufacturing of existing
products, the timing and amount of expenses, the timing and results of clinical
trials, the timing of regulatory approvals and variations in foreign exchange
rates. The Company does not have a significant backlog of customer orders, so
revenues in any quarter depend on orders received in that quarter. The Company's
expenses are relatively fixed and difficult to adjust in response to fluctuating
revenues. In addition, depending on the timing of new product introductions,
competitive factors, warranty claims and product returns, the Company may need
to reserve amounts in excess of those currently reserved for product
obsolescence, excess inventory, warranty claims and product returns. There can
be no assurance that such reserves will be adequate to cover all costs
associated with such items. In addition, quarterly results of operations may be
affected by foreign government controls, export license requirements, political
and economic instability, trade restrictions, changes in tariffs, employee
strikes or disruptions arising under foreign labor laws, standards or
guidelines, or difficulties in staffing and managing international operations.
As a result of these and other factors, the Company expects to continue to
experience significant fluctuations in quarterly operating results, and there
can be no assurance that the Company will be able to achieve or maintain
profitability in the future. See "Management's Discussion and Analysis of
Financial Condition and Results of Operations."
 
GOVERNMENT REGULATION
 
     The Company's products and operations are subject to extensive regulation
by numerous governmental authorities. In particular, the Company must obtain
specific clearance from the FDA before it can market new products or certain
modified products in the United States. The FDA administers the Federal Food,
Drug, and Cosmetic Act (the "FDC Act"). The Company has made certain
enhancements to its currently marketed products which it believes do not
necessitate the filing of a new 510(k) notification. However, there can be no
assurance that the FDA would agree with the Company's determination that these
modifications do not require a 510(k) notification. If the FDA requires the
Company to file a new 510(k) notification for any past or future modification to
a cleared device, the Company may be prohibited from marketing the device as
modified until it obtains clearance from the FDA. There can be no assurance that
the Company will obtain 510(k) clearance on a timely basis, if at all, for any
device modification. Furthermore, there can be no assurance that the Company's
future products, if any, will receive 510(k) clearance.
 
   
     FDA regulations also require companies to adhere to GMPs, which include
production design controls, testing, quality control, storage and documentation
procedures. Compliance with device GMP regulations is difficult, costly and
uncertain. The FDA may at any time inspect the Company's facilities to determine
whether adequate compliance has been achieved. There can be no assurance that
adequate compliance will be achieved or that the FDA will not withdraw marketing
clearance or require product recall or permit marketing if there is inadequate
compliance. In addition, when any change or modification is made to a device or
its intended use, the manufacturer may be required to reassess compliance with
device GMP regulations, which may cause interruptions or delays in the marketing
and sale of the Company's products. Any such interruptions or delays could have
a material adverse effect on the Company's business, financial condition and
results of operations.
    
 
                                        9
<PAGE>   11
 
     Sales of medical device products outside the United States are subject to
foreign regulatory requirements that vary from country to country. The time
required to obtain approvals required by foreign countries may be longer or
shorter than that required for FDA approval, and requirements for licensing may
differ from FDA requirements.
 
     Failure to comply with applicable federal, state or foreign laws or
regulations could subject the Company to enforcement actions, including, but not
limited to, product seizures, recalls, withdrawal of clearances or approvals and
civil and criminal penalties against the Company or its responsible officials,
any one or more of which could have a material adverse effect on the Company's
business, results of operations and financial condition. Federal, state and
foreign laws and regulations regarding the manufacture and sale of medical
devices are subject to future changes, as are administrative interpretations of
regulatory agencies. No assurance can be given that such changes will not have a
material adverse effect on the Company's business, financial condition and
results of operations. See "Business -- Government Regulation."
 
FUTURE CAPITAL NEEDS AND UNCERTAINTY OF AVAILABILITY OF ADDITIONAL FINANCING
 
     The Company believes that the anticipated net proceeds from this offering
together with interest thereon and the Company's existing capital resources will
be sufficient to fund its operations at least through 1999. However, the
Company's future liquidity and capital requirements will depend upon numerous
factors, including the resources required to further develop its marketing and
sales organization domestically and internationally, expand manufacturing
capacity, finance the Company's sales-type lease program, and meet market demand
for the Company's products. The Company's capital requirements will also depend
upon the progress of the Company's research and development programs, including
clinical trials, the receipt of and the time required to obtain regulatory
clearances and approvals, the resources the Company devotes to developing,
manufacturing and marketing its products, and the resources, if any, the Company
may devote to the expansion of its business, including through the possible
acquisition of businesses, technologies or other intellectual property rights.
There can be no assurance that the Company will not require additional financing
or will not in the future seek to raise additional funds through bank
facilities, debt or equity offerings or other sources of capital. Additional
funding may not be available when needed or on terms acceptable to the Company,
which would have a material adverse effect on the Company's business, financial
condition and results of operations. See "Use of Proceeds" and "Management's
Discussion and Analysis of Financial Condition and Results of Operations --
Liquidity and Capital Resources."
 
POTENTIAL PRODUCT LIABILITY OR RECALL
 
     The manufacture and sale of the Company's products expose it to product
liability claims and product recalls, including those which may arise from
misuse, malfunction or design flaws. There can be no assurance that the
Company's existing insurance coverage will cover the costs of any product
liability claims made against the Company or that the Company will be able to
obtain insurance in the future at satisfactory rates or in adequate amounts.
Product liability claims or product recalls, regardless of their ultimate
outcome, could result in costly litigation and could have a material adverse
effect on the Company's business, financial condition and results of operations.
See "Business -- Insurance."
 
LIMITATIONS ON THIRD-PARTY REIMBURSEMENT
 
     The Company expects that anesthesia providers will not be reimbursed
separately for patient monitoring activities utilizing the Company's BIS
monitor. For hospitals and independent ambulatory surgical centers ("ASCs"),
when reimbursement is based on charges or costs, BIS monitoring may reduce
reimbursements for surgical procedures, because charges or costs may decline as
a result of BIS monitoring. Any reduction in the reimbursement by third-party
payors to hospitals and other users as a result of using the BIS System could
limit market acceptance of the BIS System and
                                       10
<PAGE>   12
 
have a material adverse effect on the Company's business, financial condition
and results of operations.
 
POTENTIAL ADVERSE EFFECTS OF YEAR 2000 PROBLEM
 
     The Company has conducted a software review to identify functions that need
corrections to be "Year 2000" compliant. The Year 2000 problem is the result of
computer programs being written to recognize two digits rather than four to
define the applicable year causing computer programs to interpret a date using
"00" as the year 1900 rather than the year 2000, which could result in product
failures or miscalculations. The Company is undertaking certain corrective
actions in an effort to ensure that software systems incorporated in its
products or used to manage its business will continue to function properly in
the year 2000. However, there can be no assurance that Year 2000 problems will
not be encountered or that the costs incurred to resolve such problems will not
be material. Additionally, there can be no assurance that the Year 2000 problem
will not affect the Company by causing disruptions in the business operations of
persons with whom the Company does business, such as customers or suppliers.
Year 2000 problems could have a material adverse effect on the Company.
 
NO PRIOR MARKET; POSSIBLE VOLATILITY OF STOCK PRICE
 
   
     Prior to this offering, there has been no public market for the Company's
Common Stock, and there can be no assurance that an active public market for the
Common Stock will develop or continue after this offering. The initial public
offering price will be determined by negotiations among the Company and the
representatives of the Underwriters, and may not be indicative of the market
price for the Common Stock after this offering. From time to time after this
offering, there may be significant volatility in the market price of the Common
Stock. Quarterly operating results of the Company, deviations in results of
operations from estimates of securities analysts, changes in general conditions
in the economy or the medical equipment industry or other developments affecting
the Company or its competitors could cause the market price of the Common Stock
to fluctuate substantially. The equity markets have, on occasion, experienced
significant price and volume fluctuations that have affected the market prices
for many companies' securities and that have often been unrelated to the
operating performance of these companies. Any fluctuations in the equity markets
that occur following completion of this offering may adversely affect the market
price of the Common Stock. See "Underwriting."
    
 
SHARES ELIGIBLE FOR FUTURE SALE AND POTENTIAL ADVERSE EFFECT ON MARKET PRICE
 
   
     Sales of substantial amounts of shares of Common Stock in the public market
following this offering could adversely affect the market price of the Common
Stock. Upon completion of this offering, the Company will have outstanding
14,166,974 shares of Common Stock, assuming no exercise of outstanding options.
On the date of this Prospectus, in addition to the 3,100,000 shares offered
hereby, approximately 29,519 shares of Common Stock, which are not subject to
180-day lock-up agreements (the "Lock-up Agreements") with the representatives
of the Underwriters, will be eligible for immediate sale in the public market
pursuant to Rule 144(k) under the Securities Act of 1933, as amended (the
"Securities Act"). Approximately 48,945 additional shares of Common Stock which
are not subject to the Lock-up Agreements will be eligible for sale in the
public market in accordance with Rule 144 or Rule 701 under the Securities Act
beginning on the 91st day after the date of this Prospectus. Upon expiration of
the Lock-up Agreements 180 days after the date of this Prospectus, approximately
11,618,000 shares of Common Stock (including approximately 551,000 shares of
Common Stock which may be acquired upon the exercise of outstanding options)
will be available for sale in the public market, subject to the provisions of
Rule 144 under the Securities Act. BT Alex. Brown Incorporated may release any
or all shares subject to Lock-up Agreements at any time or from time to time
without notice. Approximately 180 days after the date of this Prospectus, the
Company intends to register an aggregate of approximately 4,000,000 shares of
    
 
                                       11
<PAGE>   13
 
   
Common Stock subject to present or future options under its Amended and Restated
1991 Stock Option Plan, 1998 Stock Incentive Plan, 1998 Employee Stock Purchase
Plan and 1998 Director Stock Option Plan, as amended. Holders of approximately
10,981,000 shares of Common Stock have agreed, pursuant to the Lock-up
Agreements, not to offer to sell, contract to sell, transfer, engage in any
hedging transaction with respect to or otherwise dispose of such shares for 180
days after the date of this Prospectus. The Company is unable to predict the
effect that sales made under Rule 144, or otherwise, may have on the then
prevailing market price of the Common Stock. The holders of approximately
9,400,000 shares of Common Stock are entitled to certain incidental and demand
registration rights with respect to such shares. By exercising their
registration rights, such holders could cause a large number of shares to be
registered and sold in the public market at any given time. Sales pursuant to
Rule 144 or other exemptions from registration, or pursuant to registration
rights, may have an adverse effect on the market price for the Common Stock and
could impair the Company's ability to raise capital through offerings of its
equity securities. See "Management -- Executive Compensation -- Stock Plans,"
"Shares Eligible for Future Sale" and "Underwriting."
    
 
CONTROL BY DIRECTORS, OFFICERS AND PRINCIPAL STOCKHOLDERS
 
   
     Upon completion of this offering, the Company's directors, executive
officers and principal stockholders, together with their affiliates, will
beneficially own approximately 48% of the Company's outstanding Common Stock. As
a result, these stockholders, if acting together, would have the ability to
influence or determine the outcome of corporate actions requiring stockholder
approval, including the election of directors and the approval of certain
mergers and other significant corporate transactions, such as a sale of
substantially all of the Company's assets, irrespective of how other
stockholders of the Company may vote. This concentration of ownership may have
the effect of delaying or preventing a change in control of the Company, which
could adversely affect the market price of the Company's Common Stock. See
"Management" and "Principal Stockholders."
    
 
ANTI-TAKEOVER EFFECT OF CERTAIN CHARTER, BYLAW AND OTHER PROVISIONS
 
   
     Certain provisions of the Company's Certificate of Incorporation (the
"Restated Certificate") and Bylaws, as they are each proposed to be amended and
restated concurrently with the closing of the offering, the anti-takeover
provisions of Section 203 of the Delaware General Corporation Law statute and
the automatic acceleration of the vesting of stock options and restricted stock
under certain circumstances upon a change of control, could have the effect of
delaying, deterring or preventing changes of control or management of the
Company, which could adversely affect the market price of the Company's Common
Stock. See "Description of Capital Stock."
    
 
IMMEDIATE AND SUBSTANTIAL DILUTION
 
   
     The purchasers of the shares of Common Stock offered hereby will experience
immediate and substantial dilution in the net tangible book value of their
shares of Common Stock in the amount of $9.76 per share (after giving effect to
estimated underwriting discounts and commissions and offering expenses). See
"Dilution." In the event the Company offers additional Common Stock in the
future, including shares that may be issued upon exercise of stock options,
purchasers of Common Stock in this offering may experience further dilution in
the net tangible book value per share of the Common Stock of the Company.
    
 
                                       12
<PAGE>   14
 
                                USE OF PROCEEDS
 
   
     The net proceeds to the Company from the sale of shares of Common Stock
offered hereby are estimated to be $36,629,000 ($42,250,850 if the Underwriters'
over-allotment option is exercised in full) after deducting the estimated
underwriting discounts and commissions and offering expenses payable by the
Company and assuming an initial public offering price of $13.00 per share.
    
 
     The Company expects to use the net proceeds from this offering to fund
sales and marketing, research and development efforts, the sales-type lease
program and working capital and other corporate purposes. A portion of the
proceeds of this offering may be used to acquire businesses, technologies and
other intellectual property rights and products that complement the Company's
business, although the Company has no agreements or understandings with respect
to any such potential transactions. Pending use of the net proceeds, the Company
intends to invest the net proceeds from this offering in short-term, investment
grade, interest-bearing instruments.
 
                                DIVIDEND POLICY
 
     The Company has never declared or paid any cash dividends on its capital
stock. The Company currently intends to retain earnings, if any, to support its
growth strategy and, therefore, does not anticipate paying cash dividends in the
foreseeable future. Payment of future dividends, if any, will be at the
discretion of the Company's Board of Directors after taking into account various
factors, including the Company's financial condition, operating results, current
and anticipated cash needs and plans for expansion. The Company's credit
agreement restricts the Company from declaring and paying any cash dividends.
See "Management's Discussion and Analysis of Financial Condition and Results of
Operations -- Liquidity and Capital Resources" and Note 18 of Notes to Financial
Statements.
 
                                       13
<PAGE>   15
 
                                 CAPITALIZATION
 
   
     The following table sets forth the capitalization of the Company (i) as of
July 4, 1998, and (ii) as adjusted to give effect to the conversion of all
outstanding shares of the Company's Convertible Preferred Stock into an
aggregate of 9,313,509 shares of Common Stock; the filing of the Company's
Restated Certificate to increase the number of authorized shares of Common Stock
and authorize 5,000,000 shares of authorized but undesignated preferred stock;
and to reflect the issuance and sale of 3,100,000 shares of Common Stock offered
hereby at an assumed initial public offering price of $13.00 per share, after
deducting the estimated underwriting discounts and commissions and offering
expenses payable by the Company. The capitalization information set forth in the
table below is qualified by the Financial Statements and Notes thereto appearing
elsewhere in this Prospectus.
    
 
   
<TABLE>
<CAPTION>
                                                                   JULY 4, 1998
                                                              -----------------------
                                                               ACTUAL     AS ADJUSTED
                                                              --------    -----------
                                                                  (IN THOUSANDS)
<S>                                                           <C>         <C>
Long-term debt..............................................  $    682     $    682
                                                              --------     --------
Stockholders' equity:
  Preferred stock, $.01 par value; no shares authorized,
     issued or outstanding (actual); 5,000,000 shares
     authorized, no shares issued or outstanding (as
     adjusted)..............................................        --           --
  Convertible preferred stock, $.01 par value; 18,843,224
     shares authorized (actual); 9,313,509 issued and
     outstanding (actual); (liquidation
     preference -- $41,425,301 (actual)); no shares
     authorized, issued or outstanding (as adjusted);
     (liquidation preference -- $0 (as adjusted))...........    50,300           --
  Common stock, $.01 par value; 14,500,000 shares authorized
     (actual); 1,752,965 shares issued and outstanding
     (actual); 40,000,000 shares authorized (as adjusted);
     14,166,474 shares issued and outstanding (as
     adjusted)(1)...........................................        17          141
  Additional paid-in-capital................................     1,370       88,175
  Notes receivable from employees and directors.............      (306)        (306)
  Deferred compensation.....................................      (825)        (825)
  Unrealized gain on marketable securities..................         3            3
  Accumulated deficit.......................................   (41,260)     (41,260)
                                                              --------     --------
     Total stockholders' equity.............................     9,299       45,928
                                                              --------     --------
          Total capitalization..............................  $  9,981     $ 46,610
                                                              ========     ========
</TABLE>
    
 
- ---------------
   
(1) Excludes an aggregate of 1,312,369 shares of Common Stock reserved for
    issuance pursuant to exercise of options outstanding as of July 4, 1998 at a
    weighted average exercise price of $2.07 per share. See "Management --
    Executive Compensation" and Note 9 of Notes to Financial Statements.
    
 
                                       14
<PAGE>   16
 
                                    DILUTION
 
   
     The pro forma net tangible book value of the Company as of July 4, 1998 was
approximately $9.3 million or $0.84 per share of Common Stock. Pro forma net
tangible book value per share is determined by dividing the Company's tangible
net worth (tangible assets less liabilities) by the number of shares of Common
Stock outstanding, after giving effect to the conversion of the Company's
Convertible Preferred Stock into Common Stock upon the completion of this
offering. After giving effect to the sale of the shares of Common Stock offered
by the Company hereby at an assumed initial public offering price of $13.00 per
share and after deducting the estimated underwriting discounts and commissions
and offering expenses payable by the Company, the pro forma net tangible book
value of the Company as of July 4, 1998 would have been $3.24 per share. This
represents an immediate increase in such pro forma net tangible book value of
$2.40 per share to existing stockholders and an immediate dilution of $9.76 per
share to new investors purchasing shares in this offering. If the initial public
offering price is higher or lower, the dilution to the new investors will be
greater or less, respectively. The following table illustrates the per share
dilution:
    
 
   
<TABLE>
<S>                                                           <C>     <C>
Assumed initial public offering price per share.............          $13.00
  Pro forma net tangible book value per share as of July 4,
     1998...................................................  0.84
  Increase per share attributable to new investors..........  2.40
                                                              ----
Pro forma net tangible book value per share after this
  offering..................................................            3.24
                                                                      ------
Dilution in net tangible book value per share to new
  investors.................................................          $ 9.76
                                                                      ======
</TABLE>
    
 
   
     The following table summarizes, on a pro forma basis as of July 4, 1998
(after giving effect to the conversion of the Company's Convertible Preferred
Stock upon the completion of this offering), the total number of shares of
Common Stock purchased from the Company, the total consideration paid and the
average consideration paid per share by the existing stockholders and by the new
investors based upon an assumed initial public offering price of $13.00 per
share (before deducting the estimated underwriting discounts and commissions and
offering expenses payable by the Company):
    
 
   
<TABLE>
<CAPTION>
                             SHARES PURCHASED        TOTAL CONSIDERATION       AVERAGE
                           ---------------------    ----------------------    PRICE PER
                             NUMBER      PERCENT      AMOUNT       PERCENT      SHARE
                           ----------    -------    -----------    -------    ---------
<S>                        <C>           <C>        <C>            <C>        <C>
Existing stockholders....  11,066,474     78.12%    $51,191,269     55.95%     $ 4.63
New investors............   3,100,000     21.88      40,300,000     44.05      $13.00
                           ----------    ------     -----------    ------
          Total..........  14,166,474    100.00%    $91,491,269    100.00%
                           ==========    ======     ===========    ======
</TABLE>
    
 
   
     The above information excludes an aggregate of 1,312,369 shares of Common
Stock issuable upon the exercise of options outstanding as of July 4, 1998 with
a weighted average price of $2.07 per share. To the extent that such options are
exercised there will be further dilution to new investors.
    
 
                                       15
<PAGE>   17
 
                         SELECTED FINANCIAL INFORMATION
                     (IN THOUSANDS, EXCEPT PER SHARE DATA)
 
   
     The selected financial information set forth below for the years ended
December 31, 1995, 1996 and 1997, and as of December 31, 1996 and 1997, are
derived from the Company's audited financial statements, which appear elsewhere
in this Prospectus and which have been audited, with respect to the years ended
December 31, 1996 and 1997 and as of December 31, 1996 and 1997, by Arthur
Andersen LLP, independent accountants, and with respect to the year ended
December 31, 1995, by PricewaterhouseCoopers LLP, independent accountants. The
selected financial information set forth below as of December 31, 1993, 1994 and
1995 and for the years ended December 31, 1993 and 1994 are derived from audited
financial statements, which are not included in this Prospectus. The selected
financial information for the six months ended June 28, 1997 and July 4, 1998
and as of July 4, 1998 are derived from the unaudited financial statements which
appear elsewhere in this Prospectus. In the opinion of management, the unaudited
financial statements have been prepared on a basis consistent with the Company's
audited Financial Statements which appear elsewhere in this Prospectus and
include all adjustments, consisting only of normal recurring adjustments,
necessary for a fair statement of the financial position and results of
operations for these unaudited periods. The operating results for the six months
ended July 4, 1998 are not necessarily indicative of the results to be expected
for the full year ending December 31, 1998. The information set forth below
should be read in conjunction with "Management's Discussion and Analysis of
Financial Condition and Results of Operations" and the Financial Statements and
Notes thereto, appearing elsewhere in this Prospectus.
    
 
   
<TABLE>
<CAPTION>
                                                YEAR ENDED DECEMBER 31,                  SIX MONTHS ENDED
                                  ---------------------------------------------------   ------------------
                                                                                        JUNE 28,   JULY 4,
                                    1993       1994       1995      1996       1997       1997      1998
                                  --------   --------   --------   -------   --------   --------   -------
                                                                                           (UNAUDITED)
<S>                               <C>        <C>        <C>        <C>       <C>        <C>        <C>
STATEMENTS OF OPERATIONS DATA:
  Revenue.......................  $    155   $    852   $  1,067   $ 1,389   $  3,068   $ 1,076    $ 4,420
  Costs and expenses:
    Costs of revenue............        80        525        704     1,096      3,602     1,381      2,662
    Research and development....     2,371      2,311      2,870     2,338      2,603     1,435      1,942
    Sales and marketing.........       663      1,291      1,285     1,561      4,813     1,721      4,670
    General and
      administrative............       926      1,216      1,815     1,871      2,358     1,194      1,960
                                  --------   --------   --------   -------   --------   -------    -------
      Total costs and
        expenses................     4,040      5,343      6,674     6,866     13,376     5,731     11,234
  Loss from operations..........    (3,885)    (4,491)    (5,607)   (5,477)   (10,308)   (4,655)    (6,814)
  Interest income...............       233        286        146       144        500       246        313
  Interest expense..............        (5)       (55)       (85)      (63)       (78)      (38)       (16)
                                  --------   --------   --------   -------   --------   -------    -------
  Net loss......................  $ (3,657)  $ (4,260)  $ (5,546)  $(5,396)  $ (9,886)  $(4,447)   $(6,517)
                                  ========   ========   ========   =======   ========   =======    =======
  Net loss per share(1):
    Basic and diluted...........  $(721.36)  $(822.34)  $(281.65)  $(57.76)  $ (16.23)  $(10.88)   $ (6.34)
                                  ========   ========   ========   =======   ========   =======    =======
    Pro forma basic and
      diluted...................                                             $  (1.28)             $ (0.65)
                                                                             ========              =======
  Shares used in computing net
    loss per share(1):
    Basic and diluted...........         5          5         20        93        609       409      1,027
    Pro forma basic and
      diluted...................                                                7,707                9,951
</TABLE>
    
 
   
<TABLE>
<CAPTION>
                                                                 DECEMBER 31,
                                                  ------------------------------------------     JULY 4,
                                                   1993     1994     1995     1996     1997       1998
                                                  ------   ------   ------   ------   ------   -----------
                                                                                               (UNAUDITED)
<S>                                               <C>      <C>      <C>      <C>      <C>      <C>
BALANCE SHEET DATA:
  Cash, cash equivalents and marketable
    securities..................................  $8,134   $4,258   $3,329   $2,231   $4,981     $10,131
  Working capital...............................   8,215    4,273    3,054    1,029    3,052       7,143
  Total assets..................................   8,948    5,719    4,552    3,973    7,603      16,125
  Long-term debt................................      --      423      333      270      118         682
  Total stockholders' equity....................   8,736    4,460    3,028    1,066    4,067       9,299
</TABLE>
    
 
- ---------------
(1) See Note 10 of Notes to Financial Statements.
 
                                       16
<PAGE>   18
 
                      MANAGEMENT'S DISCUSSION AND ANALYSIS
                OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS
 
     This prospectus contains certain statements of a forward-looking nature
relating to future events or the future financial performance of the Company.
Prospective investors are cautioned that such statements are only predictions
and that actual events or results may differ materially. In evaluating such
statements, prospective investors should specifically consider the various
factors identified in this Prospectus which could cause actual results to differ
materially from those indicated by such forward-looking statements, including
the matters set forth under the caption "Risk Factors."
 
OVERVIEW
 
   
     Aspect develops, manufactures and markets anesthesia monitoring systems
that enable anesthesia providers to assess levels of consciousness and
administer the appropriate amount of anesthetics during surgery. The BIS System
incorporates the Company's proprietary disposable BIS Sensors and the A-2000 BIS
Monitor, which was cleared for marketing by the FDA in February 1998. The BIS
System is based on Aspect's patented core technology, the BIS index, which is
the only FDA-cleared, commercially available, direct measure of the effects of
anesthetics on the brain. In addition to the
    
   
A-2000, the Company's other monitor products are the A-1000 monitor and the
A-1050 monitor. After the introduction of the A-2000 monitor, the Company ceased
active marketing of the A-1050 monitor in the United States. In addition to the
Company's disposable BIS Sensor, the Company offers the Zipprep EEG electrode.
    
 
   
     The Company follows a system of fiscal months as opposed to calendar
months. Under this system, the first eleven months of each fiscal year end on a
Saturday and the last month of the fiscal year always ends on December 31. All
references to the six months ended June 28, 1997 relate to the period from
January 1, 1997 to June 28, 1997, and all references to the six months ended
July 4, 1998 relate to the period from January 1, 1998 to July 4, 1998.
    
 
   
     The Company offers customers the option either to purchase the BIS monitors
outright or to acquire the BIS monitors pursuant to a sales-type lease agreement
whereby the customer contractually commits to purchase a minimum number of BIS
Sensors per BIS monitor per year. Under this agreement, customers purchase BIS
Sensors and the BIS monitor for the purchase price of the BIS Sensors plus an
additional charge per BIS Sensor to pay for the purchase price of the BIS
monitor and related financing costs over the term of the agreement. The customer
is granted an option to purchase the BIS monitor at the end of the term of the
agreement, which is typically three to five years. Revenue related to BIS
monitors sold pursuant to sales-type leases is recognized at the time of
shipment of the BIS monitors. Sales-type leases accounted for approximately 0%,
11% and 10% of revenue in 1995, 1996 and 1997, respectively, and for
approximately 12% and 30% of revenue in the six months ended June 28, 1997 and
the six months ended July 4, 1998, respectively.
    
 
   
     In 1995, 1996 and 1997, revenue from the sale of monitors and related
accessories represented approximately 94%, 87% and 80%, respectively, of the
Company's revenue, and revenue from the sale of disposables represented
approximately 6%, 13% and 20%, respectively, of the Company's revenue. In the
six months ended June 28, 1997 and the six months ended July 4, 1998, revenue
from the sale of monitors and related accessories represented approximately 79%
and 73%, respectively, of the Company's revenue, and revenue from the sale of
disposables represented approximately 21% and 27%, respectively, of the
Company's revenue. The Company expects that revenue from the sale of disposables
will continue to increase as a percentage of total revenue.
    
 
RESULTS OF OPERATIONS
 
     The following table presents, for the periods indicated, information
expressed as a percentage of revenue. Such information has been derived from the
Statements of Operations included
 
                                       17
<PAGE>   19
 
   
elsewhere in this Prospectus. The Company's past operating results are not
necessarily indicative of future operating results.
    
 
   
<TABLE>
<CAPTION>
                                                             PERCENTAGE OF REVENUE
                                                ------------------------------------------------
                                                 YEAR ENDED DECEMBER 31,      SIX MONTHS ENDED
                                                -------------------------    -------------------
                                                                             JUNE 28,    JULY 4,
                                                1995      1996      1997       1997       1998
                                                -----     -----     -----    --------    -------
<S>                                             <C>       <C>       <C>      <C>         <C>
Revenue.......................................   100%      100%      100%       100%       100%
Costs and expenses:
  Costs of revenue............................    66        79       117        128         60
  Research and development....................   269       168        85        133         44
  Sales and marketing.........................   120       112       157        160        106
  General and administrative..................   170       135        77        111         44
                                                ----      ----      ----       ----       ----
          Total costs and expenses............   625       494       436        532        254
Loss from operations..........................  (525)     (394)     (336)     (432)      (154)
Interest income...............................    13        10        16         23          7
Interest expense..............................    (8)       (5)       (2)        (4)        (1)
                                                ----      ----      ----       ----       ----
Net loss......................................  (520)%    (389)%    (322)%     (413)%     (148)%
                                                ====      ====      ====       ====       ====
</TABLE>
    
 
   
  Six Months Ended July 4, 1998 Compared to Six Months Ended June 28, 1997
    
 
   
     The Company's revenue increased to $4.4 million in the six months ended
July 4, 1998 from $1.1 million in the six months ended June 28, 1997. Revenue
from the sale of monitors and related accessories increased to $3.2 million in
the six months ended July 4, 1998 from $846,000 in the six months ended June 28,
1997, and revenue from the sale of disposables increased to $1.2 million in the
six months ended July 4, 1998 from $230,000 in the six months ended June 28,
1997. The growth in sales of monitors and related accessories was primarily
related to an increase in the number of units sold as a result of the
introduction in the United States of the A-2000 monitor and the growth of the
direct sales force. The increase in sales of disposables was primarily related
to growth in the installed base of monitors.
    
 
   
     The Company's gross profit was 40% of revenue in the six months ended July
4, 1998 as compared to a negative gross profit of 28% of revenue in the six
months ended June 28, 1997. The negative gross profit in the six months ended
June 28, 1997 resulted primarily from under-absorbed overhead costs and
provisions for excess and obsolete inventory. The increase in gross profit in
the six months ended July 4, 1998 as compared to the six months ended June 28,
1997 was primarily due to lower per-unit monitor costs and improved
manufacturing efficiencies.
    
 
   
     Research and development expenses increased to $1.9 million in the six
months ended July 4, 1998 from $1.4 million in the six months ended June 28,
1997, but decreased as a percentage of revenue. The absolute dollar increase was
primarily attributable to continued product development efforts related to the
A-2000 monitor, development of products for use outside the OR, an increase in
expenses related to clinical studies and an increase in research and development
personnel.
    
 
   
     Sales and marketing expenses increased to $4.7 million in the six months
ended July 4, 1998 from $1.7 million in the six months ended June 28, 1997, but
decreased as a percentage of revenue. The increase in absolute dollars was due
to an increase in sales and marketing personnel and an increase in advertising
and market development expenses associated with a promotion program for the BIS
monitor initiated by the Company in 1998.
    
 
   
     General and administrative expenses increased to $2.0 million in the six
months ended July 4, 1998 from $1.2 million in the six months ended June 28,
1997, but decreased as a percentage of revenue. The absolute dollar increase was
primarily attributable to an increase in general and administrative personnel to
support the Company's growth.
    
 
   
     Interest income increased to $313,000 in the six months ended July 4, 1998
from $246,000 in the six months ended June 28, 1997. The increase in interest
income was due to a higher average outstanding cash and investments balance
resulting from sales of the Company's Convertible
    
 
                                       18
<PAGE>   20
 
   
Preferred Stock in February 1997 and February 1998. Interest expense decreased
to $16,000 in the six months ended July 4, 1998 from $38,000 in the six months
ended June 28, 1997 as a result of lower average outstanding capital lease
obligations in the six months ended July 4, 1998.
    
 
  Year Ended December 31, 1997 Compared to Year Ended December 31, 1996
 
   
     The Company's revenue increased to $3.1 million in 1997 from $1.4 million
in 1996. Revenue from the sale of monitors and related accessories increased to
$2.5 million in 1997 from $1.2 million in 1996 and revenue from the sale of
disposables increased to $606,000 in 1997 from $181,000 in 1996. The increase in
revenue from the sale of monitors and related accessories was primarily
attributable to the commercial introduction of the A-1050 monitor in 1996 and
the increase in the growth of the direct sales force in 1997. The increase in
revenue from the sale of disposables was primarily attributable to the
commercial introduction of the BIS Sensor in 1997 and growth in the installed
base of monitors. In 1996, the Zipprep electrode was the Company's only
disposable product.
    
 
     In 1997, the Company had a negative gross profit percentage of 17% as
compared to a gross profit percentage of 21% in 1996. The negative gross profit
in 1997 and the decrease in gross profit as compared to 1996 resulted primarily
from under-absorbed overhead costs and provisions for excess and obsolete
inventory.
 
     Research and development expenses increased to $2.6 million in 1997 from
$2.3 million in 1996, but decreased as a percentage of revenue in 1997 as
compared to 1996. The absolute dollar increase in 1997 was primarily due to the
new product development efforts related to the A-2000 monitor and the BIS Module
Kit.
 
     Sales and marketing expenses increased to $4.8 million in 1997 from $1.6
million in 1996. This increase was primarily due to an increase in sales and
marketing personnel, including the establishment of the clinical specialist
group, and the related costs of compensation, benefits and travel expenses.
 
     General and administrative expenses increased to $2.4 million in 1997 from
$1.9 million in 1996, but decreased as a percentage of revenue in 1997 as
compared to 1996. The absolute dollar increase was primarily attributable to an
increase in general and administrative personnel to support the Company's
growth.
 
     Interest income increased to $500,000 in 1997 from $144,000 in 1996 due to
an increase in the average outstanding cash and investments balance resulting
from the sale of the Company's Convertible Preferred Stock in February 1997.
Interest expense increased to $78,000 in 1997 from $63,000 in 1996 as a result
of higher average outstanding capital lease obligations in 1997.
 
  Year Ended December 31, 1996 Compared to Year Ended December 31, 1995
 
     The Company's revenue increased to $1.4 million in 1996 from $1.1 million
in 1995. Revenue from the sale of monitors and related accessories increased to
$1.2 million in 1996 from $1.0 million in 1995, and revenue from the sale of
disposables increased to $181,000 in 1996 from $67,000 in 1995. The increase in
revenue from the sale of monitors and related accessories was primarily
attributable to the commercial introduction of the A-1050 monitor in 1996. The
increase in revenue from the sale of disposables was primarily attributable to
growth in the installed base of monitors.
 
     The Company's gross profit was 21% of revenue in 1996 as compared to 34% of
revenue in 1995. The decrease from 1995 to 1996 was primarily attributable to a
lower average selling price on the A-1050 monitor introduced in 1996 compared to
the A-1000 monitor.
 
     Research and development expenses decreased to $2.3 million in 1996 from
$2.9 million in 1995. This decrease resulted from a reduction in research and
development personnel in the second half of 1995.
 
                                       19
<PAGE>   21
 
     Sales and marketing expenses increased to $1.6 million in 1996 from $1.3
million in 1995, but decreased as a percentage of revenue. The absolute dollar
increase was primarily due to an increase in advertising and marketing expenses
related to the introduction of the A-1050 monitor.
 
     General and administrative expenses increased to $1.9 million in 1996 from
$1.8 million in 1995, but decreased as a percentage of revenue in 1996 as
compared to 1995. The absolute dollar increase was primarily attributable to an
increase in general and administrative personnel to support the Company's
growth.
 
     Interest income remained relatively constant between 1995 and 1996.
Interest expense decreased from $85,000 in 1995 to $63,000 in 1996. The lower
interest expense in 1996 was primarily due to lower average outstanding capital
lease obligations.
 
QUARTERLY RESULTS OF OPERATIONS
 
   
     The following table sets forth unaudited selected operating results for
each of the six fiscal quarters in the period ended July 4, 1998. The Company
believes that the following selected quarterly information includes all
adjustments (consisting only of normal, recurring adjustments) that the Company
considers necessary to present this information fairly. This financial
information should be read in conjunction with the Company's Financial
Statements and Notes thereto appearing elsewhere in this Prospectus. These
operating results are not necessarily indicative of results for any future
period.
    
 
   
<TABLE>
<CAPTION>
                                                          QUARTER ENDED
                             ------------------------------------------------------------------------
                             MARCH 29,   JUNE 28,   SEPTEMBER 27,   DECEMBER 31,   APRIL 4,   JULY 4,
                               1997        1997         1997            1997         1998      1998
                             ---------   --------   -------------   ------------   --------   -------
                                                          (IN THOUSANDS)
<S>                          <C>         <C>        <C>             <C>            <C>        <C>
Revenue....................   $   415    $   661       $   845        $ 1,147      $ 1,733    $ 2,687
Net loss...................    (2,166)    (2,281)       (2,409)        (3,030)      (2,817)    (3,700)
</TABLE>
    
 
LIQUIDITY AND CAPITAL RESOURCES
 
   
     Since its inception, the Company has financed operations primarily from the
sale of its Convertible Preferred Stock. Through July 4, 1998, the Company had
raised approximately $50.3 million from equity financings and had received $1.2
million in equipment lease financing. At July 4, 1998, the Company had
approximately $165,000 committed to the purchase of equipment related to the
automation of the BIS Sensor production line.
    
 
   
     Working capital at July 4, 1998 was approximately $7.1 million compared to
approximately $3.1 million and approximately $1.0 million at December 31, 1997
and 1996, respectively. The increase in working capital from December 31, 1997
to July 4, 1998 was primarily due to the sale of the Company's Convertible
Preferred Stock in February 1998, and increases in accounts receivable,
investment in sales-type leases and inventory, offset by increases in accounts
payable, accrued liabilities and deferred revenue. The increase in working
capital from 1996 to 1997 was primarily due to the sale of the Company's
Convertible Preferred Stock in February 1997, and an increase in accounts
receivable, offset by a decrease in inventory and increases in accounts payable
and accrued liabilities.
    
 
   
     The Company used approximately $6.1 million of cash for operations in the
six months ended July 4, 1998. Cash used for operations during this period was
primarily driven by operating losses, increases in accounts receivable,
investment in sales-type leases and inventory, offset by increases in accounts
payable, accrued liabilities and deferred revenue. The Company used
approximately $17.5 million for operations during the three years ended December
31, 1997. Cash used for operations during this period was also primarily driven
by operating losses, increases in accounts receivable and investment in
sales-type leases, offset by increases in accounts payable, accrued liabilities
and deferred revenue.
    
 
                                       20
<PAGE>   22
 
   
     The Company used approximately $3.4 million of cash for investing
activities in the six months ended July 4, 1998. The Company invested
approximately $2.2 million, net, in marketable securities and approximately $1.1
million in manufacturing equipment, leasehold improvements and new information
systems. The Company used approximately $3.0 million for investing activities
during the three years ended December 31, 1997. The Company invested
approximately $1.2 million, net, in marketable securities and approximately $1.8
million in manufacturing equipment, leasehold improvements and new information
systems.
    
 
   
     The Company received approximately $12.4 million of cash from financing
activities in the six months ended July 4, 1998 primarily as a result of the
sale by the Company of its Convertible Preferred Stock in February 1998. The
Company received approximately $20.1 million of cash from financing activities
during the three years ended December 31, 1997. Cash provided by financing
activities during this period was primarily the result of the sale by the
Company of its Convertible Preferred Stock in each of the three years.
    
 
   
     In June 1998, the Company entered into a loan agreement with a commercial
bank. Under the terms of this loan agreement, the Company may borrow up to $5.0
million for working capital and equipment. The amount available to the Company
under the working capital portion of the loan agreement is based upon a
percentage of the Company's outstanding accounts receivable. The outstanding
principal under the working capital portion of the loan agreement is due and
payable in December 1999. The principal amount outstanding under the equipment
portion of the loan agreement is due in 36 equal monthly installments commencing
January 1999. At July 4, 1998, approximately $776,000 was outstanding under the
equipment portion of the loan agreement.
    
 
     The Company has conducted a software review to identify functions that need
corrections to be "Year 2000" compliant. The Year 2000 problem is the result of
computer programs being written to recognize two digits rather than four to
define the applicable year causing computer programs to interpret a date using
"00" as the year 1900 rather than the year 2000, which could result in product
failures or miscalculations. The Company is undertaking certain corrective
actions in an effort to ensure that software systems incorporated in its
products or used to manage its business will continue to function properly in
the year 2000. However, there can be no assurance that Year 2000 problems will
not be encountered or that the costs incurred to resolve such problems will not
be material. Additionally, there can be no assurance that the Year 2000 problem
will not affect the Company by causing disruptions in the business operations of
persons with whom the Company does business, such as customers or suppliers.
Year 2000 problems could have a material adverse effect on the Company.
 
     The Company believes that the financial resources available to it,
including its current working capital and loan agreement, together with the net
proceeds of this offering, will be sufficient to finance its planned operations
and capital expenditures at least through 1999. However, the Company's future
liquidity and capital requirements will depend upon numerous factors, including
the resources required to further develop its marketing and sales organization
domestically and internationally, to expand manufacturing capacity, to finance
the Company's sales-type lease program and to meet market demand for the
Company's products.
 
                                       21
<PAGE>   23
 
                                    BUSINESS
 
THE COMPANY
 
   
     Aspect develops, manufactures and markets anesthesia monitoring systems
that enable anesthesia providers to assess levels of consciousness and
administer the appropriate amount of anesthetics during surgery. The BIS System
incorporates the Company's proprietary disposable BIS Sensors and the A-2000 BIS
Monitor, which was cleared for marketing by the FDA in February 1998. The BIS
System is based on Aspect's patented core technology, the BIS index, which is
the only FDA-cleared, commercially available direct measure of the effects of
anesthetics on the brain. The BIS System was developed over a ten-year period
and is the subject of eight issued and five pending United States patents.
Aspect markets the BIS System through a direct sales organization in the United
States. As of July 4, 1998, more than 880 BIS monitors have been sold to
approximately 140 sites in the United States, and the Company believes that over
150,000 patients have been monitored using the BIS index during surgery.
    
 
MARKET OPPORTUNITY
 
     The three basic objectives of general anesthesia are to render the patient
unconscious, to prevent response to painful stimuli and to ensure the patient
will not move during the surgical procedure. A combination of drugs is typically
used to accomplish these goals, including drugs to induce unconsciousness,
analgesics to provide pain relief and muscle relaxants to immobilize the
patient. Historically, anesthesia providers have had no direct means of
assessing a patient's level of consciousness during surgery and have generally
relied on recommended drug dosages and on indirect indicators of consciousness,
including blood pressure and heart rate. Changes in these indirect measures,
however, are not reliable indicators of changes in a patient's level of
consciousness. Although anesthesia providers can adjust recommended anesthetic
dosages based on individual patient characteristics, these adjustments cannot
always account for variability in patient responses to anesthesia or changes in
anesthetic requirements during the course of surgery.
 
   
     Each year, approximately 29 million patients in the United States and 42
million patients in Europe and Japan receive anesthesia for surgical procedures,
of whom more than 60% receive general anesthesia or deep sedation monitored by
an anesthesia provider. In the United States, there are approximately 34,000 ORs
in hospitals and 5,000 in independent ambulatory ASCs. In Europe and Japan,
there are approximately 48,000 ORs in hospitals.
    
 
     Third-party payors and managed care organizations are increasingly
scrutinizing the high cost of surgical care. As a result, hospitals are
implementing programs to control surgical costs, including the cost of
anesthetic drugs and anesthesia recovery, while seeking to improve quality of
care and safety. Programs to accelerate the anesthesia recovery process include
reducing the amount of time patients remain in the OR following the completion
of surgery, reducing the amount of time patients are required to remain in the
Post Anesthesia Care Unit ("PACU") after surgery, and allowing a higher
percentage of patients to bypass the PACU following ambulatory surgery and
proceed immediately to less costly step-down recovery areas.
 
     The Company believes that providing an effective tool for monitoring a
patient's level of consciousness during surgery will contribute to improving the
quality, safety and efficiency of anesthesia care. Using existing monitoring
devices, anesthesia providers are sometimes unable to identify surgical
awareness, or the unintentional regaining of consciousness during surgery,
because anesthetized patients who have received muscle relaxants are unable to
communicate and because changes in vital signs are not reliable indicators of
changes in levels of consciousness. It is estimated that, in the United States,
surgical awareness occurs in approximately 0.2% of surgeries requiring general
anesthesia, or approximately 35,000 procedures per year.
 
     Because of variations in the amount of anesthetic drugs administered for
any given surgery, variations in patient tolerances to anesthetic drugs and the
desire to prevent surgical awareness, the
                                       22
<PAGE>   24
 
Company believes that anesthesia providers tend to administer more anesthetic
than is required by many of their patients. Overmedication contributes to the
high cost of surgical care as a result of increased drug costs, prolonged and
unpredictable wake-ups from anesthesia and prolonged post-anesthesia recovery in
the PACU. These factors, in turn, lead to inefficiencies in OR and PACU
scheduling and increased personnel costs.
 
     In addition to the OR, anesthesia is administered to sedate patients in
ICUs and for diagnostic and therapeutic procedures outside the OR. Many patients
admitted to the ICU receive sedation during their stay. There are approximately
80,000 beds in hospitals in the United States for critical care patients and
over 22 million patient days per year are spent in the ICU. The assessment of a
patient's level of sedation in the ICU is subjective, relies on indirect
measures, and is usually carried out by several different individuals in a
24-hour period, many of whom are not trained in anesthesia. The Company believes
that this may result in overmedication that may extend the patient's length of
stay in the ICU.
 
     Advances in pharmacology and the development of less-invasive diagnostic
and therapeutic procedures have enabled physicians to perform more procedures
outside the OR under conscious sedation rather than general anesthesia. Aspect
estimates that in the United States there are approximately 42,000 rooms in
hospitals, ASCs and doctors' offices where these procedures are performed.
During conscious-sedation procedures, a trained anesthesia provider may or may
not be present depending on the institution's policies and the attending
physician's judgment. One of the risks of conscious sedation is that
overmedication may cause a patient to lose consciousness and fall into a state
of general anesthesia resulting in the loss of protective reflexes, including
the ability to breath without mechanical assistance.
 
THE ASPECT SOLUTION: PATIENT MONITORING WITH THE BIS INDEX
 
     The Company has developed the only FDA-cleared, commercially available
product for use as a direct measure of anesthetic effect on the brain. Aspect's
clinically validated BIS index assists the anesthesia provider in assessing
levels of consciousness and administering appropriate amounts of anesthesia
required for the surgical procedure while avoiding unintentional overmedication
or undermedication. Company-sponsored clinical trials have shown that
administering appropriate levels of anesthetics results in less drug use, and
therefore, lower drug costs, faster wake-up from anesthesia, less patient time
in the OR and the PACU following surgery and improvement in the quality of
recovery. Other studies have shown that when appropriate levels of anesthesia
are administered, patients are more likely to meet criteria for bypassing the
PACU following ambulatory surgery and proceeding immediately to the less costly
step-down recovery area. The Company also believes that the BIS index can be
used to assess the risk of surgical awareness.
 
   
     The BIS index is a numerical index derived from the combination of several
processed EEG variables that correlate with loss of consciousness and changes in
levels of sedation. The BIS System, which incorporates the BIS index, is
comprised of the Company's BIS monitor and single-use, disposable BIS Sensors.
The FDA cleared for marketing the BIS index for use as a direct measure of
anesthetic effect on the brain in October 1996 and cleared the A-2000 BIS
Monitor in February 1998.
    
 
     The following are examples of the benefits of BIS monitoring demonstrated
by the Company in a 302-patient prospective, randomized, controlled clinical
utility trial:
 
     - More controlled and cost-effective dosing of anesthetic drugs:  Patients
       monitored with the BIS index during surgery received 23% less anesthetic
       than patients who were not BIS monitored. Based upon the current average
       cost of the anesthetic drugs used in this utility trial, the Company
       believes that the use of the BIS index could result in drug cost savings
       of up to $18.00 per case.
 
     - Faster and more predictable recovery from anesthesia:  Patients receiving
       BIS monitoring during surgery emerged from unconsciousness 35% to 40%
       faster than patients who did not
 
                                       23
<PAGE>   25
 
       receive BIS monitoring. In addition, only 5% of BIS-monitored patients
       required more than 15 minutes to emerge from anesthesia compared with 16%
       of patients who did not receive BIS monitoring. Moreover, patients who
       received BIS monitoring were eligible for discharge from the PACU 16%
       faster than patients who did not receive BIS monitoring.
 
     - Improved quality of recovery:  Patients received better clinical
       assessments of their recovery by PACU nurses when the BIS index was used.
       In addition, 43% of patients monitored with the BIS index were alert and
       oriented when admitted to the PACU, as compared to 23% of patients not
       monitored with the BIS index during surgery.
 
     The Company believes that the BIS index also provides an effective
indication of the risk of surgical awareness. The Company demonstrated the
correlation of BIS index values with the loss of and return to consciousness in
two clinical efficacy studies, one involving approximately 100 volunteers and
one involving 40 patients. The Company estimates that more than 100,000 patients
have been monitored with the BIS index during surgery. Four cases of surgical
awareness with BIS monitoring have been reported to the Company. In each case,
high BIS index values were noted, indicating that the BIS index correctly
identified the potential risk of awareness in these patients. The Company has
not undertaken the clinical studies necessary to confirm that BIS monitoring
reduces the incidence of surgical awareness because the Company estimates that
surgical awareness typically occurs in only one patient per 500 and, therefore,
the required studies are not practicable.
 
STRATEGY
 
   
     The BIS index is the only FDA-cleared and commercially available measure of
the effects of anesthetics on the brain. Aspect's objective is to become a major
multinational anesthesia monitoring company by establishing BIS monitoring as
the standard of practice in anesthesia and sedation monitoring. Key elements of
the Company's strategy to accomplish its objective include the following:
    
 
   
     Direct Sales Force for Rapid Commercialization.  Aspect intends to
capitalize on its first-to-the-market position by pursuing a rapid
commercialization strategy that emphasizes use of a direct sales force. The
Company believes that a direct sales force is best able to convey to anesthesia
providers and administrators the clinical benefits and potential cost savings
achievable with BIS monitoring. Flexible sales options allow hospitals to either
purchase BIS monitors outright or acquire BIS monitors by committing to purchase
a minimum number of BIS Sensors per monitor per year. As of July 4, 1998, the
Company has sold more than 880 BIS monitors to approximately 140 sites in the
United States and the Company believes that over 150,000 patients have been
monitored with the BIS Sensor.
    
 
   
     Clinical Specialists to Educate and to Promote the Use of Aspect's BIS
System.  Aspect intends to establish a ratio of 1.5 clinical specialists for
each of the Company's sales representatives. The principal responsibilities of
these clinical specialists are to provide education, training and support for
the Company's installed base and to promote appropriate use of BIS Systems.
These activities are designed to increase the use of BIS Sensors in the OR. The
Company expects that clinical specialists will also play a key role in expanding
the use of BIS monitoring to markets outside the OR, including the ICU and
conscious-sedation markets.
    
 
     OEM Relationships to Broaden Distribution Channels.  The Company believes
that original equipment manufacturer ("OEM") relationships will accelerate
market penetration of the BIS technology. OEM relationships will result in
integration of the BIS index into third-party patient-monitoring systems. The
Company currently is a party to two OEM agreements and expects to enter into
additional OEM relationships with patient-monitoring or medical device companies
over the next several years to expand the channels for distribution of the BIS
System, particularly in international markets.
 
                                       24
<PAGE>   26
 
     Technological Leadership.  Aspect's priority is to improve current
applications of BIS technology and to develop further its signal-processing
technology. In addition, the Company intends to continue to sponsor and support
research of leading clinicians to further document the clinical utility of the
BIS index. The Company intends to protect its intellectual property and
technology leadership position through product innovation, patents and other
proprietary means.
 
     New Product Development.  The Company is continuing to focus both on
product extensions, such as the application of the BIS index for the ICU and
conscious-sedation markets, and on new product development, such as the
application of bispectral analysis to the electrocardiogram (the "ECG"). Each of
these initiatives builds on the Company's core expertise and innovations in
signal-processing technology. Continued innovation and commercialization of new
proprietary products is an essential element in the Company's long-term growth
strategy and the source of potential competitive advantages.
 
PRODUCTS
 
     The following chart summarizes Aspect's product offerings, all of which
have received 510(k) clearance from the FDA:
 
   
<TABLE>
<CAPTION>
                                           INITIAL
                                          COMMERCIAL
                PRODUCT                    SHIPMENT                     DESCRIPTION
                -------                  ------------                   -----------
<S>                                      <C>             <C>
A-2000 BIS Monitor                       March 1998      Small, lightweight third-generation BIS
                                                         monitor for the OR
BIS Sensor                               1997            Single-piece, single-use disposable
                                                         product for use with A-2000, A-1050 and
                                                         BIS Module Kit
BIS Module Kit(1)                        --              Components of BIS monitoring technology to
                                                         be integrated into OEM monitors
A-1050 EEG Monitor with BIS              1996            Second-generation monitor with BIS index
                                                         and simplified user interface
A-1000 EEG Monitor                       1993            Aspect's first commercial EEG monitor with
                                                         BIS index
Zipprep EEG Electrode                    1995            EEG electrode with Aspect's Zipprep
                                                         technology used with A-1000 monitor
</TABLE>
    
 
- ---------------
(1) The Company has commenced commercial shipment of the BIS Module Kit. The
    Company does not believe any OEM has commenced commercial shipment of its
    BIS Module product. Each OEM will be required to obtain FDA clearance of its
    BIS Module product.
 
  A-2000 BIS Monitor
 
   
     Aspect began commercial distribution of the A-2000 BIS Monitor ("A-2000"),
the Company's third-generation monitoring product, in March 1998. The A-2000 is
a compact, portable monitor designed to accommodate the space limitations and
positioning requirements of surgical settings. The A-2000 displays the BIS index
and supporting information on a high-contrast electro-luminescent display and
includes Aspect's proprietary Digital Signal Converter. The Digital Signal
Converter is a palm-sized module that performs the analog-to-digital conversion
of the EEG and provides the interface between the monitor and the BIS Sensor,
which adheres to the patient's forehead. The A-2000 is compact (7 inches by 6.8
inches by 4 inches) and lightweight (3.1 pounds). The hardware architecture of
the A-2000 employs a 50 megaflops floating-point processor to perform the BIS
index computation and a 25 MIPS RISC processor to perform the user-interface
functions. The list price for the A-2000 is $8,900.
    
 
                                       25
<PAGE>   27
 
  BIS Sensor
 
     The BIS Sensor is a single-piece, single-use disposable product for use
with the A-2000, the A-1050 and the BIS Module Kit. Aspect's BIS monitors and
BIS Module Kits require the use of the BIS Sensor to generate the BIS index. The
BIS Sensor provides a reliable and simple means of acquiring the high-resolution
EEG signal needed to generate the BIS index. The one-piece design allows quick
and accurate placement on the patient's forehead. The BIS Sensor connects to the
monitor by a single-point proprietary connector. The Company commenced
commercial shipment of the BIS Sensor in January 1997. The list price for the
BIS Sensor is $15.00.
 
   
     Aspect's Zipprep self-prepping technology is a key feature of the BIS
Sensor because it minimizes patient set-up time and enables consistent, accurate
readings of the EEG signal. Prior to Aspect's development of the Zipprep
technology, to obtain an EEG signal the user prepared a patient's skin by
rubbing an abrasive cream over the area 10 to 20 times in order to remove the
top layer of skin. The Zipprep technology contains a non-conductive polymer disk
with multiple, small, flexible tines that are embedded in a standard electrode
hydrogel. As a function of their design, the Zipprep tines come in contact with
and part the outer layer of dead cells on the skin. This allows the electrode's
hydrogel to quickly penetrate the skin and establish an effective electrical
contact to the patient.
    
 
  BIS Module Kit
 
     In 1996, Aspect introduced the BIS Module Kit, which requires the use of
the BIS Sensor in order to calculate the BIS index. The BIS Module Kit is
designed to facilitate the integration of the Company's BIS index into
monitoring products marketed by third parties that enter into OEM arrangements
with the Company. The Company is currently a party to two OEM agreements.
 
     The BIS Module Kit consists of two pieces, the Company's proprietary
Digital Signal Converter and a small circuit board that resides in the OEM
equipment. The Digital Signal Converter acquires the EEG signal from the BIS
Sensor, performs the analog-to-digital conversion, and transmits the digitized
EEG signal to the circuit board. The circuit board then processes the EEG signal
and outputs the BIS index to the OEM system.
 
     The Company expects that all OEM licensees of the BIS index technology will
use the common architecture of the BIS Module Kit, which will facilitate
integration of the BIS index into the OEM's system and will simplify any future
software updates of the BIS index technology.
 
TECHNOLOGY
 
     Aspect's BIS System was developed over a ten-year period and combines the
computational power of bispectral analysis with proprietary signal-processing
algorithms. The BIS index is a numerical index derived from the combination of
several processed EEG variables that correlate with loss of consciousness and
changes in levels of sedation. The EEG, the electrical signal generated in the
cortex of the brain, changes in response to anesthetic drugs. In general, the
EEG changes from a low-amplitude, high-frequency signal while a person is awake
to a large-amplitude, low-frequency signal while a person is deeply
anesthetized. Mathematical algorithms based on this observation, such as the
Spectral Edge Frequency and Median Frequency, attempt to track the effects of
anesthetics on the brain. However, these processed EEG parameters have not been
widely adopted because studies have indicated that they generally do not provide
sufficient clinically useful information to assess levels of consciousness with
commonly used anesthetic agents and doses.
 
     In developing the BIS index, the Company sought to improve these early EEG
analyses in two ways. First, by using bispectral analysis, a mathematical tool
that examines non-linear signals such as the EEG, new information is extracted
from the EEG signal. The second improvement involves the development of
proprietary processing algorithms that extract information from bispectral
analysis, power spectral analysis and time domain analysis. Bispectral analysis
was originally used in the early
 
                                       26
<PAGE>   28
 
1960s by geophysicists to study ocean wave motion, atmospheric pressure changes
and seismic activity. Bispectral analysis can now be utilized for other
applications with the advent of high-speed, low-cost digital signal processors.
This technology is based on the non-linear expansion of Fourier analysis, which
provides the means to analyze the frequency, amplitude and phase relationships
within a signal. As a result, a distinctive "fingerprint" of the underlying
process that generates the signal can be obtained. Bispectral analysis extracts
this unique fingerprint and represents it as a three-dimensional mathematical
model of the signal's structure.
 
     The Company created the BIS index to describe changes in the EEG that
relate to the effects of anesthetics on the brain in order to assess levels of
consciousness. Over a number of years, a large database of high-fidelity EEG
recordings and clinical assessments were collected by the Company and third
parties from patients and volunteers receiving a wide variety of anesthetic
agents. The clinical assessments used to define levels of consciousness included
a sedation-rating scale, picture or word recall memory tests, and response to
stimuli. Using statistical methods, Aspect identified features within the EEG
that correlated with sedation and loss of consciousness. The Company used
proprietary multivariate statistical methods to combine these features to
generate an interpretive numerical index, which the Company refers to as the BIS
index. The BIS index ranges from 100, indicating that the patent is awake, to
zero, indicating an absence of electrical brain activity.
 
CLINICAL DEVELOPMENT
 
     The Company's clinical and regulatory affairs research group (i)
establishes collaborative relationships with leading clinical researchers; (ii)
encourages publications related to the BIS index in the scientific literature;
(iii) is responsible for clinical research with the goal of extending the
application of BIS monitoring to other settings and clinical uses; and (iv)
collects data for new product development. The Company has a clinical database
of over 5,000 cases for use in algorithm development and product validation
based on trials conducted or sponsored by the Company or undertaken by third
parties.
 
     In 1996, the FDA cleared for marketing the Company's BIS index as a measure
of anesthetic effect on the brain. The regulatory process involved studies
conducted by the Company on over 900 subjects. These studies characterized the
relationships between the BIS index value and various clinical endpoints,
including movement response to incision, response to verbal command as a measure
of consciousness in volunteers and patients, memory function, drug utilization
and speed of patient recovery following surgery.
 
     The Company evaluated the use of BIS monitoring as a measure of sedation,
consciousness and memory function in two clinical trials. In a multicenter study
involving approximately 100 volunteers, the Company demonstrated that the BIS
index correlated with the level of responsiveness and tracked the loss of
consciousness. In a second trial involving 40 patients, the BIS index reliably
correlated with the return to consciousness after a single injection of either
propofol or thiopental, two anesthetics often used to induce unconsciousness.
Several studies conducted by third parties, some of which were partially funded
by the Company, have generally confirmed these results.
 
   
     The Company's multicenter, prospective, randomized, controlled clinical
utility trial of 302 patients demonstrated the outcome benefits of BIS
monitoring. This trial compared clinical outcomes of a group of BIS-monitored
patients to a similar group of patients who were monitored under standard
clinical practice without BIS monitoring. The principal efficacy endpoints were
the amounts of anesthetic given and the speed of recovery following surgery.
BIS-monitored patients received 23% less propofol, woke up earlier in the
operating room, were more likely (43% versus 23%) to arrive at the PACU fully
alert and oriented, were judged by PACU nurses to have had better recovery and
met criteria for discharge from the PACU sooner.
    
 
     Following FDA clearance of the BIS index, there have been five additional
prospective, randomized, clinical studies of BIS monitoring. The studies, one of
which was conducted by the Company, evaluated the effectiveness of BIS
monitoring in conjunction with various commonly used
                                       27
<PAGE>   29
 
anesthetic agents on a total of nearly 300 patients. Each of the five studies
indicated that BIS monitoring led to a statistically significant reduction,
ranging from 15% to 38%, in the amount of anesthetic used per patient.
 
   
     One of the third-party studies, which was partially funded by the Company,
evaluated whether patients monitored with the BIS index were more likely to
bypass the PACU and proceed directly to the step-down recovery unit following
surgery. In this 60-patient study, approximately 90% of the BIS-monitored
patients were considered eligible to bypass the PACU as compared to 63% of
patients who were not BIS monitored.
    
 
     In 1997, the Company's outcome study of 1,552 patients documented the
clinical impact and cost-effectiveness of routine BIS monitoring in all
operating rooms of Grady Hospital, a high-acuity, urban hospital located in
Atlanta, Georgia and affiliated with Emory University. Patients received a wide
variety of anesthetic agents typically used in general practice. Comprehensive
data were collected on all patients who received general anesthesia for at least
one hour. Results demonstrated that maintaining BIS index values within a
recommended target range during anesthetic maintenance was associated with
improved outcomes in terms of drug utilization, OR and PACU recovery and
associated costs.
 
     There are more than 175 scientific articles and abstracts reporting the
results of BIS index performance in studies conducted by the Company and third
parties. In addition, Aspect currently maintains collaborations with over 50
clinical research sites.
 
SALES, MARKETING AND CUSTOMERS
 
   
     The Company markets its BIS Systems in the United States through a direct
sales force. As of July 4, 1998, the Company's domestic sales force was
comprised of 15 sales professionals and 16 clinical specialists. Aspect has
developed a financial model for use by sales representatives to assist
administrators in evaluating the economic impact of BIS monitoring at their
hospital. Aspect believes that its clinical specialists play a key role in the
ongoing process of developing support for the BIS technology both before and
after the sale of BIS Systems. The principal responsibilities of clinical
specialists are clinical training and education at the time the equipment is
installed. Clinical specialists also make follow-up visits at each customer site
at regularly scheduled intervals. These visits allow clinical specialists to
monitor customer satisfaction and provide continuing feedback to the Company's
marketing and research and development staffs. The Company also believes that
these visits may help to establish BIS monitoring as the standard of practice in
anesthesia monitoring and to extend BIS monitoring into other settings in the
hospital, such as the ICU and conscious-sedation procedure rooms. Clinical
specialists generally have nursing backgrounds and have experience in
anesthesia, perioperative care or critical care. The Company currently plans to
hire several additional sales representatives and clinical specialists prior to
the end of 1998. The Company intends to establish a ratio of 1.5 clinical
specialists for each of the Company's sales representatives.
    
 
     The Company offers customers the option either to purchase the BIS monitors
outright or to acquire the BIS monitors pursuant to a sales-type lease agreement
whereby the customer contractually commits to purchase a minimum number of BIS
Sensors per BIS monitor per year. Under this agreement, customers purchase the
BIS Sensors and the BIS monitor for the purchase price of the BIS Sensors plus
an additional charge per BIS Sensor to pay for the purchase price of the BIS
monitor and related financing costs over the term of the agreement. The customer
is granted an option to purchase the BIS monitor at the end of the term of the
agreement, which is typically three to five years. The Company believes that the
sale-type lease arrangement in some cases reduces the time required for
customers to adopt the BIS System because it provides them with an option to
utilize their operating budget to fund the purchase.
 
     The Company's customers include anesthesia providers, hospitals, ASCs and
individual practitioners in office-based practice. The key customers that the
Company has targeted initially include
                                       28
<PAGE>   30
 
   
the larger hospitals and ASCs, at or near capacity, with a high ratio of
outpatient surgical procedures to total surgical procedures. Through July 4,
1998, approximately 140 sites in the United States have acquired the BIS System.
    
 
     The Company conducts several activities for the different constituencies
that may be involved in the decision-making process. For clinical audiences, the
Company exhibits at tradeshows, sponsors speakers at professional meetings and
develops articles for publication in conjunction with industry experts. To
educate consumers and hospital administrators, the Company is conducting a
public-relations campaign to highlight the benefits of BIS monitoring for
hospitals and patients. In addition, the Company works with hospitals to
publicize their adoption of BIS monitoring in an effort to assist them in
communicating their commitment to improving the quality and efficiency of
patient care. The Company believes that such publicity in the local media allows
hospitals to compete more effectively in their service areas and has allowed
Aspect to expand its business in those markets.
 
     In January 1998, the Company entered into a three-year distribution
agreement with Nihon Kohden pursuant to which the Company granted to Nihon
Kohden Corporation ("Nihon Kohden") exclusive rights to distribute the Company's
BIS monitors in Japan. The import and sale of the Company's BIS monitors by
Nihon Kohden is subject to approval by the Japanese Ministry of Health and
Welfare. Nihon Kohden applied for this approval in early 1998.
 
     The Company has hired a president of its newly-developed International
Division and is evaluating several options for international distribution of its
products, including the development of a field organization that includes sales
representatives and clinical specialists in selected countries and international
regions. The Company is also evaluating entering into distribution agreements
with dealers, distributors and anesthesia monitoring companies outside the
United States.
 
RESEARCH AND DEVELOPMENT
 
     The Company's research and development efforts focus primarily on
continuing to improve the function and features of the BIS System and enhancing
the Company's technical leadership in signal-processing technology for use in
patient care. The Company intends to leverage the BIS technology for the
development of new monitoring products and proprietary disposables for new
applications.
 
   
     During the fiscal years ended December 31, 1995, 1996 and 1997, and the six
months ended July 4, 1998, the Company expended $2.9 million, $2.4 million, $2.6
million and $1.9 million, respectively, in its research and development efforts,
including clinical and regulatory expenses. The Company expects research and
development expenses to increase in the future as it seeks to enhance its
existing products and develop additional products. As of July 4, 1998, the
Company employed 16 persons in its research and development group and eight
persons in its clinical and regulatory group. For a further discussion of the
Company's clinical and regulatory group, see "-- Clinical Development."
    
 
     The Company conducts research and development in five areas: algorithm
research, product development, disposable-product development, pre-production
quality assurance and clinical engineering. Algorithm research involves
developing signal-processing techniques to analyze the EEG and other
biopotentials. Product-development activities include developing the hardware
and software, including signal-processing software employed in the Company's BIS
Systems, and coordinating with external resources, particularly with respect to
mechanical engineering and industrial design. Disposable-product research and
development combines expertise in materials science, disposable-products design,
electrode technology and design for manufacturing to develop the Company's
disposable products, including the BIS Sensor products. Pre-production quality-
assurance activities include testing the Company's products to ensure that they
meet FDA guide-
 
                                       29
<PAGE>   31
 
lines, other applicable regulatory and international quality standards and
internal verification and validation protocols.
 
     The Company is currently seeking to improve the BIS index technology for
ICU applications. Sedative agents are frequently used on ICU patients to reduce
anxiety, to enhance patient compliance to various interventional treatments and
to improve patient comfort. The current methods of assessing levels of sedation
in the ICU rely on a variety of indirect, often subjective, assessments
performed by observing physical signs and patient responsiveness to voice or
touch. These assessments are typically carried out by a number of different
health care providers in a 24-hour period, many of whom are not trained in
anesthesia. Patients in the ICU often have a critical illness or injury that
affects one or more organ systems simultaneously resulting in high degrees of
variability in patient responses to drug doses. Another complicating problem in
assessing a patient's level of sedation in the ICU is the effect of muscle
relaxants. These drugs may render the assessment extremely difficult because the
patient's ability to respond to the observer is eliminated due to drug-induced
paralysis. There are reports of patients who do not receive adequate levels of
sedation when these agents are used. In these cases, patients are paralyzed and
subjected to painful and traumatic therapies while the clinician is unaware of
the patient's discomfort. The Company is currently evaluating monitoring
products intended to measure the effects of sedation in the ICU setting.
 
     The Company is also enhancing the BIS index for use in procedures requiring
sedation that are performed outside the OR. In these procedures, the level of
conscious sedation required ranges from light to deep sedation. The types of
procedures where conscious sedation is used include diagnostic endoscopy for
upper gastrointestinal exams, colonoscopy, bronchoscopy, and cystoscopy;
diagnostic and therapeutic radiological procedures, oral surgery, plastic
surgery, interventional cardiac procedures, and some emergency-room procedures.
During these procedures, a trained anesthetist may not be present depending upon
the local institution's policies and the attending physician's judgment. One of
the risks of conscious sedation is that overmedication may cause a patient to
lose consciousness and fall into a state of general anesthesia resulting in the
loss of protective reflexes, including the ability to breath without mechanical
assistance.
 
     The Company is exploring the development of a BIS Sensor with improved
signal-processing systems for detection and filtration of noise in settings
outside the OR and other BIS Sensors which offer advantages in cases where
patients may require extended BIS monitoring, such as in the ICU.
 
     The Company is also conducting preliminary research on the application of
its BIS index technology to ECG signals to diagnose cardiovascular disease. The
Company believes that bispectral analysis may provide a means for extracting and
quantifying subtle physiological information contained in the ECG and thus has
the potential to enhance the diagnostic accuracy of many ECG applications,
including the early diagnosis and assessment of coronary artery disease, a more
rapid assessment of acute myocardial infarctions and advanced perioperative
ischemia monitoring for patients at risk for heart attacks during or after
surgery.
 
     Additional studies, sponsored in part by the Company, are ongoing to assess
the performance of the BIS index in the presence of certain anesthetics, such as
ketamine, and patient populations, such as children, not included in the
clinical development of the BIS algorithms. There can be no assurance that the
BIS technology will be effective in monitoring these or other anesthetic agents
and patient populations or when other anesthetic techniques are used.
Furthermore, there can be no assurance that the Company will be successful in
developing any product enhancements or extensions or new products, including
products for use in the ICU, for conscious sedation or for other applications.
The failure of the Company to develop product enhancements or extensions or new
products on a timely basis or at all could have a material adverse effect on the
Company's business, financial condition and results of operations. See "Risk
Factors -- Technological Risks."
 
                                       30
<PAGE>   32
 
MANUFACTURING
 
   
     The Company assembles all of its BIS monitors in a 7,000 square foot
manufacturing facility located within its Natick, Massachusetts headquarters.
The Company has historically outsourced the manufacturing of its BIS Sensors. In
the first quarter of 1998, the Company transitioned a portion of its production
of BIS Sensors to its manufacturing facility. The Company currently outsources
to third parties the production of some of its BIS Sensors and all of its
Zipprep electrodes. The Company is currently building a custom-designed,
semi-automated production line for the high-volume manufacture of its BIS
Sensors that it expects to be operational by late 1998. The Company may require
additional manufacturing capacity within the next two years. The Company will
seek to obtain additional manufacturing facilities as needed. While the Company
believes that additional space on reasonable commercial terms will be available
to meet its future manufacturing needs, there can be no assurance that the
Company will be successful in expanding its manufacturing facility or relocating
its facility to meet demand in a timely manner or within budget.
    
 
     The Company's production process for its BIS monitors consists of final
assembly, integration and testing of standard and custom components. The
Company's production process for its BIS Sensors consists of several
manufacturing and assembly processes using custom components. Qualified
sub-contractors, who have met the Company's supplier certification process and
are placed on an approved vendors list, produce certain custom components.
 
     The Company maintains a quality-assurance program covering its
manufacturing operations. Suppliers of purchased components are required to meet
stated specifications. The Company certifies suppliers prior to use by
conducting audits and product inspections. The Company engages in ongoing
evaluations of the performance of its suppliers by evaluating the results of
inspections and tests as well as the timeliness of product deliveries. The
Company employs numerous quality-assurance procedures during its in-house
manufacturing processes to ensure finished products meet specification.
Quality-assurance procedures include operator training, process validation,
equipment calibration, inspection and testing. All manufacturing procedures and
processes are formally approved and updated using established revision-control
procedures. Documentation of in-process and final-testing results is maintained
in device history records for every unit. The Company maintains an ongoing
post-sale performance-monitoring program.
 
     Although most of the standard components utilized by the Company in
manufacturing its products are available from more than one vendor, certain key
components of the Company's BIS Systems, including certain components used in
the BIS Sensor, are currently provided to the Company by single or limited
sources. A significant unplanned event at a supplier, including shortages of raw
materials or components, could have a material adverse effect on the Company's
operations. In addition, any termination or modification of any manufacturing
arrangement with a third party could result in a business interruption for the
Company. The Company has only one manufacturing facility, and any loss of,
damage to, or interruption of production at its facility could have a material
adverse effect on the Company's business, financial condition and results of
operations. See "Risk Factors -- Limited Manufacturing Experience; Manufacturing
Expansion."
 
COMPETITION
 
     The medical device market is highly competitive and characterized by rapid
product development and technological advances. The future success of the
Company will depend in part upon its ability to anticipate and keep pace with
advancing technology and competitive innovations. However, there can be no
assurance that the Company will be successful in identifying, developing and
marketing new products or enhancing its existing products. In addition, there
can be no assurance that new monitoring products or alternative techniques for
evaluating the effects of anesthesia or other significant changes in the methods
of delivering anesthesia will not be developed that will render the Company's
current or planned products obsolete or inferior. Rapid technological
development by competitors may result in the Company's products becoming obso-
 
                                       31
<PAGE>   33
 
lete before the Company recovers a significant portion of the research,
development and commercialization expenses incurred with respect to such
products.
 
     Although the BIS monitor is currently the only device to be cleared by the
FDA for use in the United States as a direct measure of anesthetic effect on the
brain, the Company expects to face significant competition in the future. The
Company believes that competition will initially come from companies, including
patient monitoring companies, currently marketing conventional EEG monitors
utilizing standard signal-processing techniques such as the Spectral Edge
Frequency and Median Frequency, or companies that market EEG monitors utilizing
novel signal-processing technologies, including at least two companies that are
currently conducting clinical trials on products under development.
Additionally, a number of academic researchers worldwide are studying the
potential use of other techniques to measure the effects of anesthesia,
including the use of auditory evoked potentials, heart rate variability,
pupillary reflexes and skin blood flow measurement techniques. In addition, the
Company may face substantial competition from companies developing sensor
products that are competitive with the Company's proprietary BIS Sensors for use
with the Company's BIS monitors. Competitors in some jurisdictions outside the
United States may enter the market without the delay caused by regulatory
barriers that exist in the United States. Many potential competitors have
substantially greater financial, marketing, technical, manufacturing and
distribution resources than those of the Company. In addition, the Company will
compete on the basis of a number of factors in areas in which the Company has
limited experience, including manufacturing efficiencies, marketing and sales
capabilities and customer service. There can be no assurance that the Company
will be able to compete successfully against competitors or that competition,
including the development and commercialization of new products and technology,
will not have a material adverse effect on the Company's business, financial
condition or results of operations. See "Risk Factors -- Competition."
 
PATENTS AND PROPRIETARY RIGHTS
 
   
     The Company's policy is to prosecute and enforce its patents and
proprietary technology. The Company intends to continue to file United States
and foreign patent applications to protect technology, inventions and
improvements that are considered important to the development of its business.
The Company also relies upon trade secrets, know how, continuing technological
innovation and licensing opportunities to develop and maintain its competitive
position. As of July 4, 1998, the Company held eight United States patents and
several foreign patents and had filed five additional United States patent
applications and numerous patent applications in certain major industrial
countries, including Canada, the major European market countries, Australia and
Japan.
    
 
   
     The Company has established a substantial proprietary position with respect
to its core signal-processing technology, bispectral analysis, and its
application to biological signals. A series of four issued United States patents
covers the application of bispectral and higher order analysis to EEG signals,
along with various statistical-modeling techniques. Two United States patent
applications cover innovative methods of ensuring the reliability of the
computed values; of these, one has been allowed but has not yet issued and the
other is pending. The Company also holds two issued United States patents
covering the application of its core technology to ECG applications. The Company
holds one United States patent and three United States patent applications
covering its proprietary electrode and sensor technology. The issued patent
covers the Company's Zipprep self-prepping disposable electrode technology, a
patent application covers the Company's proprietary sensor interconnection
technology, and two other patent applications cover the Company's proprietary
disposable BIS Sensor technology. The Company owns a United States patent that
covers signal acquisition technology for the Company's Digital Signal Converter
and has been granted a perpetual, royalty-free, non-exclusive license to a
second United States patent covering this technology by a third party.
    
 
     The Company believes that its competitive position and success has depended
on, in part, and will continue to depend on the ability of the Company to obtain
patent protection for its products, to
                                       32
<PAGE>   34
 
defend patents once obtained, to preserve its trade secrets and to operate
without infringing upon patents and proprietary rights held by third parties,
both in the United States and in foreign countries. There can be no assurance
that the Company has or will develop or obtain additional rights to products or
processes that are patentable, that patents will issue from any of the pending
patent applications filed by the Company or that claims allowed will be
sufficient to protect the Company's technology or technology that is licensed to
the Company. In addition, no assurances can be given that any patents issued to
the Company will not be challenged, invalidated, infringed or circumvented or
that the rights granted thereunder will provide competitive advantages for the
Company's business or products. Protection of patent rights outside the United
States could be more costly and result in a greater diversion of effort and
resources of management than protection of patent rights inside the United
States. In such event, the business, results of operations and financial
condition of the Company could be materially adversely affected.
 
     There has been substantial litigation regarding patent and other
intellectual property rights in the medical devices industry. The Company has in
the past been involved in patent litigation and future litigation may be
necessary to protect patents, trade secrets, copyrights or "know-how" owned by
the Company or to defend the Company against claimed infringement of the rights
of others and to determine the scope and validity of the proprietary rights of
the Company and others. The validity and breadth of claims covered in medical
technology patents involve complex legal and factual questions for which
important legal principles are unresolved. Any such litigation could result in
substantial cost to and diversion of effort by the Company. Adverse
determinations in any such litigation could subject the Company to significant
liabilities to third parties, could require the Company to seek licenses from
third parties with unfavorable terms, if at all, and could prevent the Company
from manufacturing, selling or using certain of its products, any of which could
have a material adverse effect on the Company's business, results of operations
and financial condition.
 
     The Company also relies on copyrights, trade secrets and proprietary
technology that it seeks to protect, in part, through confidentiality agreements
with employees, consultants and other parties. There can be no assurance that
these agreements will not be breached, that the Company will have adequate
remedies for any breach, that others will not independently develop
substantially equivalent proprietary information or that third parties will not
otherwise gain access to the Company's trade secrets.
 
     The Company also relies upon trademarks and trade names for the development
and protection of brand loyalty and associated goodwill in connection with its
products. The Company's policy is to protect its trademarks, trade names and
associated goodwill by, among other methods, filing United States and foreign
trademark applications relating to its products and business. The Company owns
numerous United States and foreign trademark registrations and applications. The
Company's registered and unregistered trademark rights relate to the majority of
the Company's products. There can be no assurance that any registered or
unregistered trademarks or trade names owned by or licensed to the Company or
licensed to the Company will not be challenged, cancelled, infringed,
circumvented, be declared generic or infringing of other third-party marks or
provide any competitive advantage to the Company. The Company also is a party to
a license agreement with a third party pursuant to which it has obtained the
nonexclusive right to make, use and/or sell products under the name "Aspect."
The licensor of the Aspect name markets monitors for use in the healthcare
industry. There can be no assurance that there will not be confusion in the
market between the Company and such licensor. In addition, there can be no
assurance that other companies in the medical device industry will not emerge
with the same or a similar name and thereby create confusion in the market or
that any such confusion would compromise the competitive advantage, if any, the
Company derives from its name.
 
GOVERNMENT REGULATION
 
     The manufacture and sale of medical diagnostic devices intended for
commercial distribution and use are subject to extensive government regulation
in the United States and in other countries.
                                       33
<PAGE>   35
 
The Company's existing products are regulated in the United States as medical
devices by the FDA under the Federal Food, Drug, and Cosmetic Act ("FDC Act").
Pursuant to the FDC Act, the FDA regulates the research, testing, manufacturing,
safety, labeling, storage, record keeping, advertising, distribution and
production of medical devices. Noncompliance with applicable regulations can
result in failure of the government to grant clearance for devices, withdrawal
of prior clearances or approvals, total or partial suspension of production,
fines, injunctions, civil penalties, recall or seizure of products and criminal
prosecution.
 
   
     Generally, before the Company can introduce a new product in the United
States, the Company must obtain FDA clearance of a premarket notification under
Section 510(k) of the FDA Act ("510(k)") or approval of a PMA application under
Section 515 of the FDC Act. To date, the Company has received 510(k) clearance
from the FDA with respect to the following products: A-1000 (December 1992);
Zipprep EEG Electrodes (June 1994); A-1050 (January 1996); BIS Sensor (October
1996); BIS Clinical Utility Indication (October 1996) and A-2000 (February
1998). While the Company has been successful to date in obtaining regulatory
approval of its products through the 510(k) notification process, there can be
no assurance that any of the Company's future products will meet the
requirements for 510(k) clearance. If the FDA concludes that any product does
not meet such requirements, then a PMA would be required and the process for
obtaining regulatory approval would be significantly delayed.
    
 
     Once 510(k) clearance has been received, any products manufactured or
distributed by the Company are subject to extensive and continuing regulation by
the FDA, including compliance with GMP regulations, recordkeeping requirements,
reporting of adverse experience with the use of the device, post-market
surveillance, and other actions deemed necessary by the FDA. A new 510(k)
notification is also required when a medical device manufacturer makes a change
or modification to a legally marketed device that could significantly affect the
safety or effectiveness of the device, or where there is a major change or
modification in the intended use of the device. When any change or modification
is made to a device or its intended use, the manufacturer must make the initial
determination whether the change or modification is of a kind that would
necessitate the filing of a new 510(k) notification. The FDA's regulations
provide only limited guidance for making this determination. The Company has
made certain enhancements to its currently marketed products which it believes
do not necessitate the filing of a new 510(k) notification. There can be no
assurance that the FDA would agree with the Company's determinations that these
modifications do not require 510(k) notification. If the FDA requires the
Company to file a new 510(k) notification for any past or future modification to
a cleared device, the Company may be prohibited from marketing the device as
modified until it obtains clearance from the FDA. There can be no assurances
that the Company will obtain 510(k) clearance on a timely basis, if at all, for
any device modification.
 
     The FDC Act regulates the Company's quality control and manufacturing
procedures by requiring the Company to demonstrate and maintain compliance with
GMPs, including Quality Systems Regulations, as specified by the FDA. This
regulation requires, among other things, that (i) the product development and
manufacturing process be controlled by the use of written procedures and (ii)
the ability to produce devices which meet the manufacturer's specifications be
validated by extensive and detailed testing of every aspect of the process. The
regulation also requires investigation of any deficiencies in the manufacturing
process or in the products produced and detailed record keeping. The GMP
regulations are applicable to manufacturers that produce components specifically
for use in a medical device, and require design controls and maintenance of
service records.
 
     The FDA monitors compliance with GMP by conducting periodic inspections of
manufacturing facilities. If violations of applicable regulations are noted
during FDA inspections of the Company's manufacturing facilities, the continued
marketing of the Company's products may be adversely affected.
 
                                       34
<PAGE>   36
 
     The GMP regulations are subject to change and depend heavily on
administrative interpretations. There can be no assurance that future changes in
regulations or interpretations made by the FDA or other regulatory bodies, with
possible retroactive effect, will not adversely affect the Company. In August
1996, the FDA conducted a routine inspection of the Company's manufacturing
facility to ensure compliance with GMP regulations. The FDA noted no adverse
observations during this inspection. The Company believes that it has continued
to maintain manufacturing facilities and procedures that are fully compliant
with all applicable government quality systems regulations and guidelines.
However, adverse findings during future FDA facility inspections could have
material adverse effects on the Company's business, financial condition, and
result of operations.
 
     Sales of medical device products outside the United States are subject to
foreign regulatory requirements that vary from country to country. The time
required to obtain approvals required by foreign countries may be longer or
shorter than that required for FDA approval, and requirements for licensing may
differ from FDA requirements. Failure to comply with foreign regulatory
requirements could have a material adverse effect on the Company's business,
financial condition and results of operations.
 
     In June 1998, the Company obtained ISO 9001/EN46001 international quality
systems registration, a certification showing that the Company's procedures and
manufacturing facilities comply with standards for quality assurance and
manufacturing process control. The ISO 9001 certification, along with the
EN46001, the European Medical Device Directive ("MDD") certification, signifies
compliance with the requirements enabling the Company to affix the CE Mark to
its current products. The CE Mark denotes conformity with European standards for
safety and allows certified devices to be placed on the market in all European
Union countries. After June 1998, medical devices may not be sold in European
Union countries unless they display the CE Mark. However, there can be no
assurance that the Company will be able to maintain regulatory approvals or
clearances for its products in foreign countries. See "Risk
Factors -- Government Regulation."
 
     The Company has established a dedicated regulatory and quality assurance
group to maintain regulatory compliance and manage all quality-assurance
activities for the Company. This group is responsible for all regulatory
submissions and communications, scheduling and performing company-wide audits,
coordinating product update procedures and corrective actions, and maintaining
document control activities. Other quality-related responsibilities include
complaint handling, adhering to appropriate procedures and applicable
requirements related to the FDA's quality systems regulations, and coordinating
appropriate documentation for FDA and ISO 9001/EN 46001 review and audits.
 
THIRD-PARTY REIMBURSEMENT
 
     Third-party payors such as Medicare, Medicaid, private health insurance
carriers, managed care organizations, health care administration authorities in
foreign countries and other organizations may affect the pricing or demand for
the Company's products by regulating the maximum amount of reimbursement
provided for by such payors to the anesthesia providers, hospitals, ASCs or
physician's offices where surgical procedures are performed.
 
     The Company does not expect that anesthesia providers will be separately
reimbursed for patient monitoring activities utilizing the Company's BIS
monitor. When providers, such as hospitals or ASCs, are reimbursed a fixed fee
calculated on a per case, per stay, or per capita basis, which is typical for
inpatient hospital procedures and procedures performed in ASCs, the cost of BIS
monitoring will not be recovered by these providers unless the incremental costs
of BIS monitoring are offset by savings in other costs, such as the costs of
anesthetic drugs or costs of the OR or PACU. There can be no assurance that BIS
monitoring will result in sufficient savings to offset these costs. When
reimbursement is based on charges or costs, BIS monitoring may have the effect
of reducing reimbursement because the charges or costs for surgical procedures,
including OR and PACU charges and costs, may decline as a result of BIS
monitoring. Failure by hospitals and other users of
 
                                       35
<PAGE>   37
 
the BIS Systems to obtain sufficient reimbursement from third-party payors, or
any reduction in the reimbursement by third-party payors to hospitals and other
users as a result of using the BIS System, could limit market acceptance of the
BIS System and have a material adverse effect on the Company's business, results
of operations and financial condition. See "Risk Factors -- Limitations on
Third-Party Reimbursement."
 
EMPLOYEES
 
   
     As of July 4, 1998, the Company had 103 full-time employees. Approximately
16 persons were engaged in research and development activities, 21 persons were
engaged in manufacturing and engineering, eight persons were engaged in clinical
and regulatory affairs, 41 persons were engaged in sales and marketing and
clinical support and 17 persons were engaged in general and administrative
functions. None of the Company's employees is covered by a collective bargaining
agreement. The Company considers relations with its employees to be good.
    
 
SCIENTIFIC ADVISORS
 
     The Company utilizes a number of scientists and physicians to advise it on
scientific and medical matters, including experts in EEG monitoring,
pharmacology and anesthesia management. These individuals advise the Company
concerning its research and development programs, the design and implementation
of the Company's clinical research program, the Company's publication
strategies, the identification of market opportunities from the clinical
perspective and specific scientific and technical issues.
 
FACILITIES
 
     The Company currently leases approximately 23,000 square feet of
development, production, and administrative space in Natick, Massachusetts
pursuant to a lease which expires on October 31, 2000. The Company believes its
current facilities will be sufficient to meet the Company's needs through the
first half of 1999 and that additional space will be available at a reasonable
cost to meet the Company's space needs thereafter.
 
INSURANCE
 
   
     The business of the Company entails the risk of product liability and
product recall claims and any such claims could have an adverse impact on the
Company. The Company has taken and will continue to take what it believes are
appropriate precautions, including maintaining general liability and commercial
liability insurance policies which include adequate coverage for product
liability and product recall claims. The Company evaluates its insurance
requirements on an ongoing basis to enable it to maintain adequate levels of
coverage. However, there can be no assurance that product liability or product
recall claims will not exceed such insurance coverage limits or that such
insurance will be available on commercially reasonable terms or at all.
    
 
LITIGATION
 
     The Company is not a party to any material threatened or pending legal
proceedings.
 
                                       36
<PAGE>   38
 
                                   MANAGEMENT
 
EXECUTIVE OFFICERS AND DIRECTORS
 
   
     The executive officers and directors of the Company, their respective ages
and their positions with the Company are as follows:
    
 
   
<TABLE>
<CAPTION>
                 NAME                    AGE                         POSITION
                 ----                    ---                         --------
<S>                                      <C>    <C>
Nassib G. Chamoun......................  36     Chief Executive Officer, President and Director
J. Breckenridge Eagle..................  48     Chairman of the Board of Directors
J. Neal Armstrong......................  60     Vice President, Chief Financial Officer and
                                                Secretary
Jeffrey L. Barrett.....................  35     Vice President of Manufacturing and Operations
Boudewijn L.P.M. Bollen................  51     President - International
Philip H. Devlin.......................  41     Vice President of Research and Development
Steven H. Kane.........................  45     Vice President of Sales and Field Operations
Paul J. Manberg, Ph.D. ................  44     Vice President of Clinical, Regulatory and Quality
                                                  Assurance
Jean M. Nelson.........................  39     Vice President of Marketing
Stephen E. Coit(1).....................  50     Director
Edwin M. Kania, Jr. (2)................  41     Director
Lester John Lloyd(2)...................  62     Director
Terrance McGuire.......................  42     Director
Donald R. Stanski, M.D.(1).............  48     Director
</TABLE>
    
 
- ---------------
(1) Member of the Compensation Committee.
(2) Member of the Audit Committee.
 
   
     Mr. Chamoun is a founder of the Company and has served as a director of the
Company since 1987. Mr. Chamoun has served as President of the Company since
1996 and Chief Executive Officer since 1995. Mr. Chamoun served as Chairman of
the Board of Directors from 1987 to 1996 and as Chief Scientific Officer from
1991 to 1995. Mr. Chamoun also served as President and Chief Executive Officer
prior to 1995 at various times since founding the Company in 1987. From 1984 to
1987, Mr. Chamoun was a fellow in cardiovascular physiology at the Lown
Cardiovascular Laboratory of the Harvard School of Public Health. Mr. Chamoun
earned a bachelors degree in Electrical Engineering from Northeastern University
and a masters degree in Computer Engineering from Boston University.
    
 
   
     Mr. Eagle has served as a director of the Company from 1988 to 1991 and
from 1996 to the present. Mr. Eagle has served as Chairman of the Board of
Directors since November 1996. He served as President and Chief Operating
Officer of the Company in 1996 and served as a consultant to the Company in
1995. From 1989 to 1995, he served as President of ECS, Inc., a medical practice
management company, which he founded in 1989. From 1981 to 1988, he served as
Chief Financial Officer, Vice President and General Manager of The Health Data
Institute, Inc., a health care services company, which he co-founded. Mr. Eagle
earned a bachelors degree in Psychology and a masters degree in Public Health
from Yale University and received a masters degree in Business Administration
from Harvard Business School.
    
 
     Mr. Armstrong has served as Vice President and Chief Financial Officer of
the Company since 1996. From 1990 to 1996, he served as Vice President of
Finance, Chief Financial Officer and a director of Haemonetics, Inc., a
manufacturer of blood processing systems ("Haemonetics"). From 1985 to 1990, he
served as Vice President of Finance and Administration, Treasurer and Chief
Financial Officer at BTU International, a manufacturer of thermal processing
systems. He previously served for 14 years in senior operating and financial
positions at Texas Instruments, Inc., an
 
                                       37
<PAGE>   39
 
electronics company. Mr. Armstrong holds a bachelors degree in Business
Administration from the University of Texas and is a certified public
accountant.
 
     Mr. Barrett has served as Vice President of Manufacturing and Operations of
the Company since 1997. From 1996 to 1997, he served as Vice President of
Manufacturing at Aksys, Ltd., a developer of dialysis equipment. From 1989 to
1996, Mr. Barrett served in a variety of manufacturing and operating positions
at Haemonetics, serving most recently as its Vice President of Operations. Mr.
Barrett received a bachelors degree in Economics and Industrial Engineering from
Rutgers University and a masters degree in Business Administration from Boston
University.
 
   
     Mr. Bollen has served as President - International of the Company since
June 1998. From 1986 to June 1998, Mr. Bollen held several positions at Nellcor
Puritan Bennett, Inc., a medical device company, including Executive Vice
President for Worldwide Sales, Service and Distribution, Vice President of
European Sales and Marketing, and Vice President and Managing Director for
Europe. From 1981 to 1986, Mr. Bollen served as Vice President of Marketing and
Sales in Europe for Bentley Laboratories, Inc., a manufacturer of specialized
monitoring and medical equipment. Mr. Bollen holds the equivalent of a bachelors
degree in Hotel Business Management from the Hotel Business School in
Maastricht, Holland.
    
 
     Mr. Devlin has served as Vice President of Research and Development of the
Company since 1994 and served as Director of Product Development of the Company
from 1990 to 1994. From 1984 to 1985 and 1986 to 1990, he served as Software
Engineer and Manager of Software Engineering at Lifeline Systems, Inc., a
medical products and communications company. From 1980 to 1984, he served as
Chief Biomedical Engineer at Beth Israel Hospital in Boston, Massachusetts and
from 1985 to 1986, he served as Technical Marketing Engineer in the Medical
Product Group of Hewlett-Packard Company, a manufacturer of computers and
medical devices. Mr. Devlin holds a bachelors and masters degree in Electrical
Engineering from Northeastern University.
 
     Mr. Kane has served as Vice President of Sales and Field Operations of the
Company since 1997. From 1990 to 1997, he served as Area Vice President, Sales
and Operations, Northeastern United States at Pyxis Corp., a medical technology
company. From 1988 to 1990, he served as Regional Manager, Eastern United
States, at IVAC Corp., an intravenous infusion therapy systems company.
 
     Dr. Manberg has served as Vice President of Clinical, Regulatory and
Quality Assurance of the Company since 1991. From 1984 to 1990, he served in a
variety of clinical research positions at Serono Laboratories, a pharmaceutical
company, most recently as Vice President, Research and Development. From 1979 to
1984, he served as a Clinical Research Scientist at Burroughs-Wellcome Company,
a pharmaceutical company, and served as an Adjunct Research Scientist at the
University of North Carolina. Dr. Manberg received a bachelors degree in
Biological Sciences from the State University of New York at Binghamton and a
doctorate in Pharmacology from the University of North Carolina at Chapel Hill.
 
     Ms. Nelson has served as Vice President of Marketing of the Company since
1992. From 1988 to 1992, she was employed by Nellcor, Inc., a medical device
company, serving from 1990 to 1992 as Manager of Advanced Technologies, from
1989 to 1990 as Multi-Function Monitor Group Manager and from 1988 to 1989 as
New Products Manager. From 1984 to 1988, Ms. Nelson served as a consultant with
Bain and Company, Inc., a strategic management consulting firm. Ms. Nelson
earned a bachelors degree in Metallurgy and Materials Engineering from Lehigh
University and a masters degree in Business Administration from the University
of Chicago Graduate School of Business.
 
     Mr. Coit has served as a director of the Company since 1987. He has been a
self-employed artist since 1997. From 1995 to 1997, Mr. Coit served as a general
partner of Charles River Ventures, a venture capital firm. From 1984 to 1994,
Mr. Coit served as a general partner of Merrill, Pickard, Anderson & Eyre, a
venture capital firm. Since 1989, Mr. Coit has also served as a director of
International Data Group, a provider of media research and conferences to the
information technology industry.
 
                                       38
<PAGE>   40
 
     Mr. Kania has served as a director of the Company since 1995. Mr. Kania is
a founding general partner of OneLiberty Ventures, a venture capital firm.
Previously, he was a general partner at a predecessor firm, Morgan Holland
Ventures, which he joined in 1985. Mr. Kania is also a director of Anesta
Corporation.
 
     Mr. Lloyd has served as a director of the Company from 1991 to April 1995
and from November 1995 to the present. He served as President and Chairman of
Aradigm, Inc., a medical device company, from 1992 to 1997. From 1995 to the
present, Mr. Lloyd has also served as Chairman of the Board of Alere Medical,
Inc., a chronic disease monitoring company. Mr. Lloyd is also a director of
Molecular Dynamics, Inc.
 
     Mr. McGuire has served as a director of the Company since 1997. He has been
a general partner of Polaris Venture Partners, a venture capital firm, since
1996. From 1992 to the present, Mr. McGuire has served as general partner of
Burr, Egan, Deleage & Co., a venture capital firm, and from 1988 to the present,
he has served as general partner of Beta Partners, a venture capital firm. Mr.
McGuire is also a director of Ascent Pediatrics, Inc., Cubist Pharmaceuticals,
Inc. and Integ Incorporated.
 
   
     Dr. Stanski has served as a director of the Company since 1996. Dr. Stanski
has been a professor of anesthesia and medicine (Clinical Pharmacology) at
Stanford University since 1979 and is an anesthesiologist/clinical
pharmacologist. He served as Chair of the Department of Anesthesia at Stanford
University from 1992 to 1997. Dr. Stanski received his medical degree from the
University of Calgary, Canada, and his anesthesiology training at the
Massachusetts General Hospital.
    
 
     Pursuant to a Third Amended and Restated Voting Agreement dated February
13, 1998 among the Company and certain stockholders of the Company, certain
stockholders have the right to nominate persons as their representatives on the
Company's Board of Directors. Each of the current directors has been nominated
to serve as a director pursuant to this agreement. This agreement will terminate
concurrently with the closing of this offering.
 
   
     The Company's Restated Certificate, to be filed concurrently with the
closing of this offering, provides that the Board of Directors of the Company
will be divided into three classes, each of whose members will serve for a
staggered three-year term. The Board will consist of three Class I Directors
(Messrs. McGuire and Coit and Dr. Stanski), two Class II Directors (Messrs.
Eagle and Kania) and two Class III Directors (Messrs. Chamoun and Lloyd). At
each annual meeting of stockholders, a class of directors will be elected for a
three-year term to succeed the directors of the same class whose terms are then
expiring. The terms of the Class I Directors, Class II Directors and Class III
Directors expire upon the election and qualification of successor directors at
the annual meeting of stockholders held during the calendar years 1999, 2000 and
2001, respectively.
    
 
COMMITTEES OF THE BOARD OF DIRECTORS
 
   
     The Board of Directors has a Compensation Committee comprised of Mr. Coit
and Dr. Stanski, which makes recommendations concerning salaries and incentive
compensation for employees of and consultants to the Company and administers and
grants stock options pursuant to the Company's stock option plans. The Board of
Directors has an Audit Committee comprised of Messrs. Lloyd and Kania, which
reviews the results and scope of the annual audit, other services provided by
the Company's independent public accountants and other matters relating to
internal control systems.
    
 
DIRECTOR COMPENSATION
 
     All of the directors are reimbursed for expenses incurred in connection
with their attendance at Board of Directors and committee meetings. In addition,
non-employee directors of the Company are eligible to receive stock options
under the Company's 1998 Director Stock Option Plan.
 
     1998 Director Stock Option Plan.  The Company's 1998 Director Stock Option
Plan, as amended (the "Director Plan"), was adopted by the Board of Directors
and stockholders of the Company in February 1998. Under the terms of the
Director Plan, directors of the Company who are not employees of the Company or
any subsidiary of the Company ("Outside Directors") are eligible
 
                                       39
<PAGE>   41
 
to receive nonstatutory options to purchase shares of Common Stock. A total of
100,000 shares of Common Stock may be issued upon exercise of options granted
under the Director Plan.
 
   
     Pursuant to the Director Plan, on April 14, 1998 (the "Initial Grant
Date"), each Outside Director (other than Mr. Lloyd and Dr. Stanski) received an
option to purchase 10,000 shares of Common Stock, and each person who first
becomes an Outside Director after the Initial Grant Date will be granted an
option to purchase 10,000 shares of Common Stock on the date of his or her
initial election to the Board (the "Initial Options"). In addition, each Outside
Director shall be granted an additional option to purchase 5,000 shares of
Common Stock (the "Additional Options") on the date of each Annual Meeting of
Stockholders, commencing with the 1999 Annual Meeting of Stockholders. Each
Outside Director will be eligible to receive Additional Options if he or she is
serving as a director immediately prior to the Annual Meeting of Stockholders
and continues to serve immediately following such Annual Meeting of
Stockholders, and, if the grant date of such Additional Option is at least six
months after the Outside Director receives an Initial Option. In July 1998, the
Director Plan was amended, subject to stockholder approval, to provide that
options held by Outside Directors would vest and become fully exercisable upon a
Change of Control of the Company (as defined in the Director Plan).
    
 
     The exercise price per share of Initial Options granted on the Initial
Grant Date was $2.80. The exercise price of Initial Options granted after the
Initial Grant Date and of any Additional Options will be the closing price per
share of Common Stock on the date of grant. Initial Options are exercisable as
to one-half of the shares as of the date of grant and as to one-sixth ( 1/6th)
of the shares on the first, second and third anniversaries of the date of grant,
provided that the optionee continues to serve as a director. Additional Options
are exercisable in three equal annual installments on each of the first, second
and third anniversaries of the date of grant, provided that the optionee
continues to serve as a director. Options granted under the Director Plan
terminate on the earlier of (i) ten years from the date of grant or (ii) sixty
days after the optionee ceases to serve as a director (180 days after the
optionee ceases to serve as a director if due to death or disability).
 
EXECUTIVE COMPENSATION
 
     The following table sets forth the annual and long-term compensation for
the year ended December 31, 1997 by its Chief Executive Officer and President
and its four other most highly compensated executive officers in 1997 who were
serving as executive officers on December 31, 1997 (the Chief Executive Officer
and such other executive officers are hereinafter referred to as the "Named
Executive Officers"):
 
                           SUMMARY COMPENSATION TABLE
 
   
<TABLE>
<CAPTION>
                                                                      LONG-TERM COMPENSATION
                                               ANNUAL COMPENSATION    ----------------------
                  NAME AND                     -------------------     NUMBER OF SECURITIES
             PRINCIPAL POSITION                 SALARY      BONUS     UNDERLYING OPTIONS(1)
             ------------------                --------    -------    ----------------------
<S>                                            <C>         <C>        <C>
Nassib G. Chamoun............................  $170,000    $40,000           200,000
  Chief Executive Officer and President
J. Breckenridge Eagle........................  $157,500    $27,565                --
  Chairman of the Board of Directors
J. Neal Armstrong............................  $153,750    $26,910            70,000
  Vice President, Chief Financial Officer and
  Secretary
Steven H. Kane(2)............................  $127,153    $58,648           180,000
  Vice President of Sales and Field
  Operations
Paul J. Manberg..............................  $137,500    $24,065            50,000
  Vice President of Clinical, Regulatory and
  Quality Assurance
</TABLE>
    
 
- ---------------
(1) Represents the number of shares covered by options to purchase shares of the
    Company's Common Stock granted during the year ended December 31, 1997.
 
(2) Mr. Kane commenced employment with the Company on April 1, 1997 and received
    a salary for only nine months of the year ended December 31, 1997. His
    current annual base salary is $165,000.
 
                                       40
<PAGE>   42
 
  Option Grants During 1997
 
     The following table sets forth grants of stock options to each of the Named
Executive Officers during the year ended December 31, 1997.
 
                       OPTION GRANTS IN LAST FISCAL YEAR
 
   
<TABLE>
<CAPTION>
                                             INDIVIDUAL GRANTS                     POTENTIAL REALIZABLE VALUE
                           -----------------------------------------------------        AT ASSUMED ANNUAL
                           NUMBER OF    PERCENT OF TOTAL   EXERCISE                   RATES OF STOCK PRICE
                           SECURITIES       OPTIONS        OR BASE                      APPRECIATION FOR
                           UNDERLYING       GRANTED         PRICE                        OPTION TERM(2)
                            OPTIONS     TO EMPLOYEES IN      PER      EXPIRATION   ---------------------------
          NAME             GRANTED(1)     FISCAL YEAR       SHARE        DATE           5%            10%
          ----             ----------   ----------------   --------   ----------   ------------   ------------
<S>                        <C>          <C>                <C>        <C>          <C>            <C>
Nassib G. Chamoun........   200,000           19.2%         $0.80      11/4/07       $100,623       $254,999
J. Breckenridge Eagle....        --             --             --           --             --             --
J. Neal Armstrong........    70,000            6.7%         $0.80       9/8/07       $ 35,218       $ 89,250
Steven H. Kane...........   180,000           17.3%         $0.38      4/14/07       $ 42,450       $107,578
Paul J. Manberg..........    50,000            4.8%         $0.80       9/8/07       $ 25,156       $ 63,750
</TABLE>
    
 
- ---------------
   
(1) The dates of exercisability of the options are determined in accordance with
    their respective vesting schedules. These options vest in 48 equal monthly
    installments, provided that unvested stock options outstanding at December
    31, 2000 shall become fully exercisable on such date.
    
 
(2) Amounts reported in these columns represent amounts that may be realized
    upon exercise of the options immediately prior to the expiration of their
    term assuming the specified compound rates of appreciation (5% and 10%) on
    the market value of the Common Stock on the date of option grant over the
    term of the options. These numbers are calculated based on rules promulgated
    by the Securities and Exchange Commission and do not reflect the Company's
    estimate of future stock price growth. Actual gains, if any, on stock option
    exercises and Common Stock holdings are dependent on the timing of such
    exercise and the future performance of the Common Stock. There can be no
    assurance that the rates of appreciation assumed in this table can be
    achieved or that the amounts reflected will be received by the individuals.
 
   
  Option Exercises and Year-End Option Values
    
 
     The following table sets forth certain information regarding the aggregate
number of shares of Common Stock acquired upon option exercises by the Named
Executive Officers and the value realized upon such exercises during the year
ended December 31, 1997 and the number and value of unexercised options held by
each of the Named Executive Officers on December 31, 1997.
 
   
                         FISCAL YEAR-END OPTION VALUES
    
 
   
<TABLE>
<CAPTION>
                                                           NUMBER OF SHARES
                                                        UNDERLYING UNEXERCISED         VALUE OF UNEXERCISED
                            NUMBER OF                           OPTIONS                IN-THE-MONEY OPTIONS
                              SHARES                      AT FISCAL YEAR-END           AT FISCAL YEAR-END(2)
                             ACQUIRED       VALUE     ---------------------------   ---------------------------
NAME                      ON EXERCISE(1)   REALIZED   EXERCISABLE   UNEXERCISABLE   EXERCISABLE   UNEXERCISABLE
- ----                      --------------   --------   -----------   -------------   -----------   -------------
<S>                       <C>              <C>        <C>           <C>             <C>           <C>
Nassib G. Chamoun.......     378,964       $227,378         --         200,000                         --
J. Breckenridge Eagle...     189,482       $113,689      2,625              --        $1,575           --
J. Neal Armstrong.......     120,000       $ 72,000         --          70,000                         --
Steven H. Kane..........     180,000       $ 76,500         --              --                         --
Paul J. Manberg.........      81,207       $ 48,724         --          50,000                         --
</TABLE>
    
 
- ---------------
 
(1) Represents shares acquired upon exercise of stock options that are subject
    to repurchase by the Company. See Note 9 to Notes to Financial Statements.
 
(2) Represents the difference between the exercise price and the fair market
    value of the Common Stock at fiscal year end ($0.80) as determined by the
    Board of Directors of the Company.
 
  Stock Plans
 
   
     Amended and Restated 1991 Stock Option Plan.  The Company's Amended and
Restated 1991 Stock Option Plan (the "1991 Plan") was initially adopted by the
Board of Directors and approved by the stockholders of the Company in April
1991. As of July 4, 1998, 3,460,000 shares were
    
 
                                       41
<PAGE>   43
 
   
authorized for issuance upon exercise of outstanding options under the 1991 Plan
and options to purchase an aggregate of 1,272,369 shares of Common Stock at a
weighted average exercise price of $2.04 per share were outstanding under the
1991 Plan. On July 9, 1998, the Board of Directors decreased the number of
shares authorized for issuance upon exercise of outstanding options under the
1991 Plan to 3,360,000.
    
 
     The 1991 Plan provides for the grant of incentive stock options intended to
qualify under Section 422 of the Internal Revenue Code of 1986, as amended (the
"Code"), nonstatutory stock options, restricted stock and other stock-based
awards (collectively, "Awards").
 
     Officers, employees, directors, consultants and advisors of the Company are
eligible to receive Awards under the 1991 Plan. Under present law, however,
incentive stock options may only be granted to employees. The maximum number of
shares with respect to which an Award may be granted to any participant under
the 1991 Plan may not exceed 200,000 shares per calendar year.
 
     Optionees receive the right to purchase a specified number of shares of
Common Stock at a specified option price and subject to such other terms and
conditions as are specified in connection with the option grant. Options may be
granted at an exercise price which may be less than, equal to or greater than
the fair market value of the Common Stock on the date of grant. Under present
law, incentive stock options and options intended to qualify as
performance-based compensation under Section 162(m) of the Code may not be
granted at an exercise price less than the fair market value of the Common Stock
on the date of grant (or less than 110% of the fair market value in the case of
incentive stock options granted to optionees holding more than 10% of the voting
power of the Company). The 1991 Plan permits the Board of Directors to determine
the manner of payment of the exercise price of options, including through
payment by cash, check or in connection with a "cashless exercise" through a
broker, by surrender to the Company of shares of Common Stock, by delivery to
the Company of a promissory note, or by any combination of the permitted forms
of payment.
 
     The 1991 Plan is administered by the Board of Directors. The Board of
Directors has the authority to adopt, amend and repeal the administrative rules,
guidelines and practices relating to the 1991 Plan and to interpret the
provisions thereof. Pursuant to the terms of the 1991 Plan, the Board of
Directors may delegate authority under the 1991 Plan to one or more committees
of the Board of Directors and, subject to certain limitations, to one or more
executive officers of the Company. The Board of Directors has authorized the
Compensation Committee to administer the 1991 Plan, including the granting of
options to executive officers. Subject to any applicable limitations contained
in the 1991 Plan, the Board of Directors, the Compensation Committee or any
other committee or executive officer to whom the Board of Directors delegates
authority, as the case may be, selects the recipients of Awards and determines
(i) the number of shares of Common Stock covered by options and the dates upon
which such options become exercisable, (ii) the exercise price of options, (iii)
the duration of options, and (iv) the number of shares of Common Stock subject
to any restricted stock or other stock-based Awards and the terms and conditions
of such Awards, including the conditions for repurchase, issue price and
repurchase price.
 
   
     On July 9, 1998, the Board of Directors amended the 1991 Plan, subject to
stockholder approval, to provide that the vesting of outstanding stock options
and restricted stock held by officers, employees and directors would be
accelerated, and in certain circumstances certain stock options and shares of
restricted stock would become fully exercisable, upon a Change of Control of the
Company (as defined in the 1991 Plan).
    
 
     No Award may be granted under the 1991 Plan after April 1, 2001, but the
vesting and effectiveness of Awards previously granted may extend beyond that
date. The Board of Directors may at any time amend, suspend or terminate the
1991 Plan, except that no Award granted after an amendment of the 1991 Plan and
designated as subject to Section 162(m) of the Code by the Board of Directors
will become exercisable, realizable or vested (to the extent such amendment was
 
                                       42
<PAGE>   44
 
required to grant such Award) unless and until such amendment is approved by the
Company's stockholders.
 
   
     1998 Stock Incentive Plan.  The Company's 1998 Stock Incentive Plan (the
"Incentive Plan") was adopted by the Board of Directors on July 9, 1998, subject
to stockholder approval. The Incentive Plan is intended to replace the 1991
Plan. Up to 2,100,000 shares of Common Stock (subject to adjustment in the event
of stock splits and other similar events) may be issued pursuant to awards
granted under the Incentive Plan.
    
 
   
     The Incentive Plan provides for the grant of incentive stock options
intended to qualify under Section 422 of the Code, nonstatutory stock options,
restricted stock awards and other stock-based awards (collectively, "Awards").
    
 
   
     Officers, employees, directors, consultants and advisors of the Company and
its subsidiaries are eligible to receive Awards under the Incentive Plan. Under
present law, however, incentive stock options may only be granted to employees.
The maximum number of shares with respect to which an Award may be granted to
any participant under the Incentive Plan may not exceed 250,000 shares per
calendar year.
    
 
   
     Optionees receive the right to purchase a specified number of shares of
Common Stock at a specified option price and subject to such other terms and
conditions as are specified in connection with the option grant. Options may be
granted at an exercise price which may be less than, equal to or greater than
the fair market value of the Common Stock on the date of grant. Under present
law, incentive stock options and options intended to qualify as
performance-based compensation under Section 162(m) of the Code may not be
granted at an exercise price less than the fair market value of the Common Stock
on the date of grant (or less than 110% of the fair market value in the case of
incentive stock options granted to optionees holding more than 10% of the voting
power of the Company). The Incentive Plan permits the Board of Directors to
determine the manner of payment of the exercise price of options, including
through payment by cash, check or in connection with a "cashless exercise"
through a broker, by surrender to the Company of shares of Common Stock, by
delivery to the Company of a promissory note, or by any combination of the
permitted forms of payment.
    
 
   
     The Incentive Plan is administered by the Board of Directors. The Board of
Directors has the authority to adopt, amend and repeal the administrative rules,
guidelines and practices relating to the Incentive Plan and to interpret the
provisions thereof. Pursuant to the terms of the Incentive Plan, the Board of
Directors may delegate authority under the Incentive Plan to one or more
committees of the Board of Directors and, subject to certain limitations, to one
or more executive officers of the Company. The Board of Directors has authorized
the Compensation Committee to administer the Incentive Plan, including the
granting of options to executive officers. Subject to any applicable limitations
contained in the Incentive Plan, the Board of Directors, the Compensation
Committee or any other committee or executive officer to whom the Board of
Directors delegates authority, as the case may be, selects the recipients of
Awards and determines (i) the number of shares of Common Stock covered by
options and the dates upon which such options become exercisable, (ii) the
exercise price of options, (iii) the duration of options, and (iv) the number of
shares of Common Stock subject to any restricted stock or other stock-based
Awards and the terms and conditions of such Awards, including the conditions for
repurchase, issue price and repurchase price.
    
 
   
     The Incentive Plan provides that, unless otherwise specified, in the event
of a merger, liquidation or other Acquisition Event (as defined in the Incentive
Plan), the vesting of outstanding stock options and restricted stock would be
accelerated, and in certain circumstances certain stock options and shares of
restricted stock would become fully exercisable. In addition, in an Acquisition
Event, the Board of Directors is authorized to (i) cause all options to be
assumed by the acquiring Company; (ii) in the case of a cash acquisition, cause
all options to be accelerated and the acquiring company to pay cash to the
option holders equal to their spread; and (iii) in the case of stock options and
restricted stock that do not become fully exercisable upon an Acquisition Event,
    
                                       43
<PAGE>   45
 
   
(a) cause such options to be accelerated in full; and/or (b) cause all
restricted stock awards to become free of all restrictions.
    
 
   
     No Award may be granted under the Incentive Plan after June 2008, but the
vesting and effectiveness of Awards previously granted may extend beyond that
date. The Board of Directors may at any time amend, suspend or terminate the
Incentive Plan, except that no Award granted after an amendment of the Incentive
Plan and designated as subject to Section 162(m) of the Code by the Board of
Directors shall become exercisable, realizable or vested (to the extent such
amendment was required to grant such Award) unless and until such amendment is
approved by the Company's stockholders.
    
 
   
     1998 Employee Stock Purchase Plan.  The Company's 1998 Employee Stock
Purchase Plan (the "Purchase Plan") was adopted by the Board of Directors,
subject to stockholder approval, on July 9, 1998. The Purchase Plan authorizes
the issuance of up to a total of 150,000 shares of Common Stock to participating
employees.
    
 
   
     All employees of the Company, including directors of the Company who are
employees, and all employees of any participating subsidiaries, whose customary
employment is more than 20 hours per week and for more than five months in any
calendar year are eligible to participate in the Purchase Plan. Employees who
would immediately after the grant own 5% or more of the total combined voting
power or value of the stock of the Company or any subsidiary are not eligible to
participate in the Purchase Plan.
    
 
   
     On the first day of a designated payroll deduction period (the "Offering
Period"), the Company will grant to each eligible employee who has elected to
participate in the Purchase Plan an option to purchase shares of Common Stock as
follows: the employee may authorize an amount (a whole percentage from 1% to 10%
of such employee's base pay) to be deducted by the Company from such employee's
base pay during the Offering Period. Each Offering Period is six months. On the
last day of the Offering Period, the employee is deemed to have exercised the
option, at the option exercise price, to the extent of accumulated payroll
deductions. Under the terms of the Purchase Plan, the option price is an amount
equal to 85% of the closing price per share of the Common Stock on either the
first day or the last day of the Offering Period, whichever is lower. In no
event may an employee purchase in any one Offering Period a number of shares
which exceeds the number of shares determined by dividing $12,500 by the average
market price of a share of Common Stock on the commencement date of the Offering
Period. Employees are required to hold shares of Common Stock purchased under
the Purchase Plan for a period of one year after the end of an Offering Period.
    
 
   
     If an employee is not a participant on the last day of the Offering Period,
such employee is not entitled to exercise any option, and the amount of such
employee's accumulated payroll deductions will be refunded. An employee's rights
under the Purchase Plan terminate upon voluntary withdrawal from the Purchase
Plan at any time, or when such employee ceases employment for any reason, except
that upon termination of employment because of death, the employee's beneficiary
has certain rights to elect to exercise the option to purchase the shares which
the accumulated payroll deductions in the participant's account would purchase
at the date of death.
    
 
   
     Because participation in the Purchase Plan is voluntary, the Company cannot
now determine the number of shares of Common Stock to be purchased by any
particular current executive officer, by all current executive officers as a
group or by non-executive employees as a group.
    
 
COMPENSATION COMMITTEE INTERLOCKS AND INSIDER PARTICIPATION
 
   
     The current members of the Compensation Committee of the Board of Directors
are Mr. Coit and Dr. Stanski. No executive officer of the Company has served as
a director or member of the compensation committee (or other committee serving
an equivalent function) of any other entity, any of whose executive officers
served as a director of or member of the Compensation Committee of the Board of
Directors.
    
 
                                       44
<PAGE>   46
 
                              CERTAIN TRANSACTIONS
 
     In October 1995, certain investors, including One Liberty Fund III, L.P.
("Liberty III"), Charles River Partnership VII, Limited Partnership ("CRL VII"),
New Enterprise Associates IV, Limited Partnership ("NEA") and Catalyst Ventures,
Limited Partnership ("Catalyst"), made bridge loans to the Company in the
aggregate amount of $500,000 in exchange for promissory notes (the "October 1995
Notes"). In November 1995 and June 1996, the Company sold an aggregate of
3,800,428 shares of its Series B-1 Convertible Preferred Stock to a group of
existing and new investors, including Messrs. J. Breckenridge Eagle, the
Chairman of the Board of Directors, and J. Neal Armstrong, Vice President, Chief
Financial Officer and Secretary of the Company, Liberty III, CRL VII, NEA and
Catalyst, at a purchase price of $2.00 per share for an aggregate purchase price
of approximately $7.6 million. The purchase price was paid, in part, by the
cancellation and conversion of the October 1995 Notes. Mr. Kania, a director of
the Company, is a general partner of One Liberty Partners III, L.P., which is
the general partner of Liberty III. Mr. Coit, a director of the Company, served
as a general partner of CRL VII at the time that CRL VII purchased these
securities from the Company.
 
   
     In February 1997, August 1997 and October 1997, the Company sold an
aggregate of 3,439,949 shares of its Series C Convertible Preferred Stock to a
group of existing and new investors, including Messrs. Eagle and Armstrong,
Jeffrey L. Barrett, Vice President of Manufacturing of the Company, and Stephen
H. Kane, Vice President of Sales and Field Operations of the Company, Liberty
III, CRL VII, NEA, Orchid & Co., nominee for T. Rowe Price Threshold Fund III,
L.P. ("T. Rowe Price"), Merrill, Pickard, Anderson & Eyre IV Limited Partnership
("MPAE"), Polaris Venture Partners, L.P. ("Polaris V.P.") and Polaris Venture
Partners Founders' Fund, L.P. ("Polaris F.F."), at a purchase price of $3.75 per
share for an aggregate purchase price of approximately $12.9 million. Mr.
Jordan, who served as a director of the Company until June 1998, is a Vice
President of T. Rowe Price Associates, Inc., the general partner of T. Rowe
Price. Mr. McGuire, a director of the Company, is a member of Polaris Venture
Management Co., LLC, which is a general partner of Polaris V.P. and Polaris F.F.
    
 
   
     In February 1998, the Company issued and sold an aggregate of 1,666,234
shares of its Series D Convertible Preferred Stock to a group of existing and
new investors, including Messrs. Armstrong, Kane, Coit and Lester John Lloyd, a
director of the Company, CRL VII, Liberty III, T. Rowe Price, Polaris V.P.,
Polaris F.F. and MPAE, at a purchase price of $7.00 per share for an aggregate
purchase price of approximately $11.7 million.
    
 
   
     In February 1997, the Company entered into a Pledge Agreement with Mr.
Nassib Chamoun, the Company's Chief Executive Officer and President, pursuant to
which the Company loaned to Mr. Chamoun, on a full recourse basis, $68,214,
representing 90% of the aggregate exercise price of certain options exercised by
Mr. Chamoun. Mr. Chamoun pledged the shares of Common Stock issued upon exercise
of such options as collateral for the loan. The loan bears interest at 8% per
annum. As of July 4, 1998, $60,635 of the principal amount of the loan plus
accrued interest was outstanding.
    
 
   
     In May 1997, the Company loaned $80,000 to Mr. Chamoun. The loan is
represented by two promissory notes and is secured by a security interest in
certain securities of the Company owned by Mr. Chamoun. The loan bears interest
at 6.42% per annum. As of July 4, 1998, $70,000 of the principal amount of the
loan plus accrued interest was outstanding.
    
 
   
     In May 1997, the Company entered into a Pledge Agreement with Mr. Kane,
pursuant to which the Company loaned Mr. Kane, on a full recourse basis,
$60,750, representing 90% of the aggregate exercise price of certain options
exercised by Mr. Kane. Mr. Kane pledged the shares of Common Stock issued upon
exercise of such options as collateral for the loan. The loan bears interest at
8% per annum. As of July 4, 1998, $54,000 of the principal amount of the loan
plus accrued interest was outstanding.
    
 
                                       45
<PAGE>   47
 
   
     In September 1997, the Company loaned $27,000 to Mr. Barrett. The loan is
evidenced by a promissory note and bears interest at 8% per annum. As of July 4,
1998, the entire principal amount of the loan plus accrued interest was
outstanding. Pursuant to the terms of the promissory note, in the event that Mr.
Barrett is employed by the Company on each of September 24, 1998, 1999, 2000 and
2001, respectively, the Company will forgive the payment by Mr. Barrett of
$8,152 on each of such dates and such amounts will be considered and treated as
compensation to Mr. Barrett by the Company.
    
 
   
     In April 1998, the Company entered into a Pledge Agreement with Mr.
Barrett, pursuant to which the Company loaned to Mr. Barrett, on a full recourse
basis, $63,000, representing 90% of the aggregate exercise price of certain
options exercised by Mr. Barrett. Mr. Barrett pledged the shares of Common Stock
issued upon exercise of such options as collateral for the loan. The loan bears
interest at 8% per annum. As of July 4, 1998, the entire principal amount of the
loan plus accrued interest was outstanding.
    
 
   
     In July 1998, stock options granted under the Company's 1991 Plan during
late 1997 and early 1998 to certain officers, directors and employees of the
Company were amended to provide that any of such outstanding stock options that
are unvested at December 31, 2000 would become fully vested on such date. As a
result of such amendments, options to purchase an aggregate of 84,817 shares of
Common Stock held by officers and directors will become exercisable on December
31, 2000.
    
 
     The Company has adopted a policy providing that all material transactions
between the Company and its officers, directors and other affiliates must (i) be
approved by a majority of the members of the Company's Board of Directors and by
a majority of the disinterested members of the Company's Board of Directors and
(ii) be on terms no less favorable to the Company than could be obtained from
unaffiliated third parties.
 
                                       46
<PAGE>   48
 
                             PRINCIPAL STOCKHOLDERS
 
   
     The following table sets forth certain information regarding the beneficial
ownership of the Company's Common Stock as of July 4, 1998, and as adjusted to
reflect the sale by the Company of the shares of Common Stock offered hereby, by
(i) each person (or group of affiliated persons) who is known to the Company to
own beneficially more than 5% of the outstanding shares of Common Stock, (ii)
each of the Company's directors and Named Executive Officers, and (iii) all
directors and executive officers of the Company as a group:
    
 
   
<TABLE>
<CAPTION>
                                                                                PERCENTAGE
                                                           NUMBER OF            OWNED(1)(2)
                                                             SHARES       -----------------------
                                                          BENEFICIALLY    BEFORE THE    AFTER THE
BENEFICIAL OWNERS                                           OWNED(1)       OFFERING     OFFERING
- -----------------                                         ------------    ----------    ---------
<S>                                                       <C>             <C>           <C>
5% STOCKHOLDERS
Charles River Partnership VII, Limited Partnership......   1,580,953         14.3%         11.2%
  1000 Winter Street, Suite 3300
  Waltham, MA 02154
One Liberty Fund III, L.P.(3)...........................   1,528,096         13.8%         10.8%
  OneLiberty Ventures
  One Liberty Square
  Boston, MA 02109
Polaris Venture Partners, L.P.(4).......................   1,007,143          9.1%          7.1%
  Bay Colony Corporate Center
  1000 Winter Street, Suite 3350
  Waltham, MA 02154
New Enterprise Associates IV, Limited Partnership(5)....     654,493          5.9%          4.6%
  1119 St. Paul Street
  Baltimore, MD 21202
Orchid & Co., Nominee for T. Rowe Price
  Threshold Fund III, L.P...............................     618,382          5.6%          4.4%
  T. Rowe Price Assoc. Inc.
  100 East Pratt
  Baltimore, MD 21202
DIRECTORS AND NAMED EXECUTIVE OFFICERS
Nassib G. Chamoun(6)....................................     392,156          3.5%          2.8%
J. Breckenridge Eagle(7)................................     210,447          1.9%          1.5%
Lester John Lloyd(8)....................................      50,239            *             *
Stephen E. Coit(9)......................................       8,572            *             *
Edwin M. Kania, Jr.(10).................................   1,533,096         13.9%         10.8%
Donald R. Stanski(11)...................................      40,125            *             *
Terrance McGuire(12)....................................   1,012,143          9.1%          7.1%
J. Neal Armstrong(13)...................................     178,989          1.6%          1.3%
Steven H. Kane(14)......................................     212,322          1.9%          1.5%
Paul J. Manberg(15).....................................      92,219            *             *
All current executive officers and directors as a group
  (14 persons)(16)......................................   3,998,791         35.8%         28.0%
</TABLE>
    
 
- ---------------
    * Indicates less than 1%
 
   
 (1) Reflects the conversion, simultaneously with the closing of this offering,
     of all outstanding shares of preferred stock of the Company into an
     aggregate of 9,313,509 shares of Common Stock. The number of shares of
     Common Stock deemed outstanding after this offering includes the 3,100,000
     shares of Common Stock of the Company being offered for sale in this
    
 
                                       47
<PAGE>   49
 
   
offering. The persons and entities named in the table have sole voting and
investment power with respect to the shares beneficially owned by them, except
as noted below. Share numbers include shares of Common Stock issuable pursuant
     to outstanding options that may be exercised within the 60-day period
     following July 4, 1998.
    
 
 (2) Assumes no exercise of the Underwriters' over-allotment option.
 
 (3) Mr. Kania, a director of the Company, is a General Partner of One Liberty
     Partners III, L.P., a General Partner of Liberty III. Mr. Kania disclaims
     beneficial ownership of the shares held by Liberty III, except to the
     extent of his pecuniary interest therein.
 
   
 (4) Includes 54,829 shares held by Polaris F.F. North Star Ventures directly or
     indirectly provides investment advisory services to various venture capital
     funds, including Polaris V.P. and Polaris F.F. The general partner of these
     funds exercises sole voting and investment power with respect to the shares
     held by such funds. The principals of North Star Ventures, including Mr.
     McGuire, a director of the Company, are members of Polaris Venture
     Management Co., L.L.C. (the General Partner of both Polaris V.P. and
     Polaris F.F.). As a member of the general partner, Mr. McGuire may be
     deemed to share voting and investment power for the shares held by the
     funds. Mr. McGuire disclaims beneficial ownership of all such shares held
     by all of the aforementioned funds except to the extent of his
     proportionate pecuniary interests therein.
    
 
 (5) Includes 154,203 shares held by Catalyst. New Enterprise Associates IV,
     Limited Partnership is a General Partner of Catalyst and may be deemed to
     share voting and investment power with respect to the shares held by
     Catalyst.
 
   
 (6) Includes an aggregate of 16,666 shares of Common Stock subject to options
     which are exercisable within 60 days after July 4, 1998. Also includes
     50,000 shares of Common Stock held by The Nassib G. Chamoun 1998
     Irrevocable Trust, of which Mr. Chamoun disclaims beneficial ownership, and
     71,839 shares of Common Stock subject to repurchase by the Company under
     certain circumstances. Does not include 251,667 shares which will not
     become exercisable within 60 days of July 4, 1998.
    
 
   
 (7) Includes 35,000 shares of Common Stock held by Jeanne Warren Eagle as
     Trustee for the Trust for John Warren Eagle, of which Mr. Eagle disclaims
     beneficial ownership, and 49,828 shares of Common Stock subject to
     repurchase by the Company under certain circumstances. Does not include
     74,500 shares which will not become exercisable within 60 days of July 4,
     1998.
    
 
   
 (8) Includes an aggregate of 2,917 shares of Common Stock subject to options
     which are exercisable within 60 days after July 4 1998 and 7,986 shares of
     Common Stock subject to repurchase by the Company under certain
     circumstances. Does not include 7,083 shares which will not become
     exercisable within 60 days of July 4, 1998.
    
 
   
 (9) Includes 5,000 shares of Common Stock subject to options which are
     exercisable within 60 days after July 4, 1998. Does not include 5,000
     shares which will not become exercisable within 60 days of July 4, 1998.
    
 
   
(10) Includes 1,528,096 shares held by Liberty III. See Note 3 above. Also
     includes 5,000 shares of Common Stock subject to options which are
     exercisable within 60 days after July 4, 1998. Does not include 5,000
     shares which will not become exercisable within 60 days of July 4, 1998.
    
 
   
(11) Includes an aggregate of 20,125 shares of Common Stock subject to options
     which are exercisable within 60 days after July 4, 1998. Does not include
     24,875 shares which will not become exercisable within 60 days of July 4,
     1998.
    
 
   
(12) Includes 952,314 shares held by Polaris V.P. and 54,829 shares held by
     Polaris F.F. See Note 4 above. Also includes 5,000 shares of Common Stock
     subject to options which are exercisable within 60 days after July 4, 1998.
     Does not include 5,000 shares which will not become exercisable within 60
     days of July 4, 1998.
    
 
   
(13) Includes an aggregate of 5,834 shares of Common Stock subject to options
     which are exercisable within 60 days after July 4, 1998 and 55,000 shares
     of Common Stock subject to
    
 
                                       48
<PAGE>   50
 
   
     repurchase by the Company under certain circumstances. Does not include
     87,083 shares which will not become exercisable within 60 days of July 4,
     1998.
    
 
   
(14) Includes an aggregate of 2,083 shares of Common Stock subject to options
     which are exercisable within 60 days after July 4, 1998 and 120,000 shares
     of Common Stock subject to repurchase by the Company under certain
     circumstances. Does not include 26,667 shares which will not become
     exercisable within 60 days of July 4, 1998.
    
 
   
(15) Includes an aggregate of 14,583 shares of Common Stock subject to options
     which are exercisable within 60 days after July 4, 1998. Also includes
     3,571 shares of Common Stock held by Paul Manberg, as Custodian under the
     Uniform Transfer to Minors Act, for Shawn Joseph Manberg, 3,571 shares of
     Common Stock held by Paul Manberg, as Custodian under the Uniform Transfer
     to Minors Act, for Kate Michelle Manberg and 16,790 shares of Common Stock
     subject to repurchase by the Company under certain circumstances. Does not
     include 62,917 shares which will not become exercisable within 60 days of
     July 4, 1998.
    
 
   
(16) Includes an aggregate of 84,082 shares of Common Stock subject to options
     which are exercisable within 60 days after July 4, 1998 and 416,366 shares
     of Common Stock subject to repurchase by the Company under certain
     circumstances. Does not include 800,730 shares which will not become
     exercisable within 60 days of July 4, 1998.
    
 
                                       49
<PAGE>   51
 
                          DESCRIPTION OF CAPITAL STOCK
 
   
     As of July 4, 1998, there were outstanding an aggregate of 11,066,474
shares of Common Stock, assuming the conversion of all of the Company's
Convertible Preferred Stock, held of record by 145 stockholders.
    
 
   
     Upon closing of this offering, the authorized capital stock of the Company
will consist of 40,000,000 shares of Common Stock and 5,000,000 shares of
undesignated preferred stock, $.01 par value per share (the "Preferred Stock").
Immediately after the sale of the 3,100,000 shares of Common Stock offered
hereby, there will be 14,166,974 shares of Common Stock outstanding and no
shares of Preferred Stock outstanding.
    
 
     The following summary of certain provisions of the Common Stock and
Preferred Stock does not purport to be complete and is subject to, and qualified
in its entirety by, (i) the provisions of the Company's Restated Certificate and
amended By-Laws (to be filed and effected, respectively, on or before the
closing of this offering) and (ii) the provisions of applicable law.
 
COMMON STOCK
 
     Holders of Common Stock are entitled to one vote per share on matters to be
voted upon by the stockholders. There are no cumulative voting rights. Holders
of Common Stock are entitled to receive dividends if, as and when declared by
the Board of Directors out of funds legally available therefor. See "Dividend
Policy." Upon the liquidation, dissolution or winding up of the Company, holders
of Common Stock are entitled to share ratably in the assets of the Company
available for distribution to its stockholders, subject to the preferential
rights of any then outstanding shares of Preferred Stock. No shares of Preferred
Stock will be outstanding immediately following the closing of this offering.
The Common Stock outstanding upon the effective date of the Registration
Statement, and the shares offered by the Company hereby, upon issuance and sale,
will be fully paid and nonassessable.
 
PREFERRED STOCK
 
     Upon closing of this offering, the Company's Board of Directors will have
the authority to issue up to 5,000,000 shares of Preferred Stock in one or more
series and to fix the relative rights, preferences, privileges, qualifications,
limitations and restrictions thereof, including dividend rights, dividend rates,
conversion rights, voting rights, terms of redemption, redemption prices,
liquidation preferences, sinking fund terms and the number of shares
constituting any series or the designation of such series, without further vote
or action by the stockholders. The Company believes that the power to issue
Preferred Stock will provide flexibility in connection with possible corporate
transactions. The issuance of Preferred Stock could adversely affect the voting
power of the holders of Common Stock and restrict their rights to receive
payment upon liquidation and could have the effect of delaying, deferring or
preventing a change-in-control of the Company. See "-- Delaware Law and Certain
Charter and By-Law Provisions." The Company has no present plans to issue any
shares of Preferred Stock.
 
DELAWARE LAW AND CERTAIN CHARTER AND BY-LAW PROVISIONS
 
     The Company is subject to the provisions of Section 203 of the General
Corporation Law of Delaware. Section 203 prohibits a publicly held Delaware
corporation from engaging in a "business combination" with an "interested
stockholder' for a period of three years after the date of the transaction in
which the person became an interested stockholder, unless the business
combination is approved in a prescribed manner. A "business combination"
includes mergers, asset sales and other transactions resulting in a financial
benefit to the interested stockholder. Subject to certain exceptions, an
"interested stockholder" is a person who, together with affiliates and
associates, owns, or within three years did own, 15% or more of the
corporation's voting stock.
 
                                       50
<PAGE>   52
 
   
     The Restated Certificate, which will become effective concurrently with the
closing of this offering, provides for the division of the Board of Directors
into three classes as nearly equal in size as possible with staggered three-year
terms. See "Management." The Restated Certificate also provides that, after the
closing of this offering, any action required or permitted to be taken by the
stockholders of the Company at an annual meeting or special meeting of
stockholders may only be taken if it is properly brought before such meeting and
may not be taken by written action in lieu of a meeting. The Restated
Certificate further provides that special meetings of the stockholders may only
be called by the Chairman of the Board, the Chief Executive Officer or the Board
of Directors. Under the Company's Bylaws, in order for any matter to be
considered "properly brought" before a meeting, a stockholder must comply with
certain requirements regarding advance notice to the Company. The foregoing
provisions could have the effect of delaying until the next stockholders'
meeting stockholder actions which are favored by the holders of a majority of
the outstanding voting securities of the Company. These provisions may also
discourage another person or entity from making a tender offer for the Common
Stock, because such person or entity, even if it acquired a majority of the
outstanding voting securities of the Company, would be able to take action as a
stockholder (such as electing new directors or approving a merger) only at a
duly called stockholders' meeting, and not by written consent.
    
 
     The General Corporation Law of Delaware provides generally that the
affirmative vote of a majority of the shares entitled to vote on any matter is
required to amend a corporation's certificate of incorporation or by-laws,
unless a corporation's certificate of incorporation or bylaws, as the case may
be, requires a greater percentage. The Restated Certificate and the Bylaws
require the affirmative vote of the holders of at least 75% of the shares of
capital stock of the Company issued and outstanding and entitled to vote to
amend or repeal any of the provisions described in the prior two paragraphs.
 
     The Restated Certificate contains certain provisions permitted under the
General Corporation Law of Delaware relating to the liability of directors. The
provisions eliminate a director's liability for monetary damages for a breach of
fiduciary duty, except in certain circumstances involving wrongful acts, such as
the breach of a director's duty of loyalty or acts or omissions which involve
intentional misconduct or a knowing violation of law. Further, the Restated
Certificate contains provisions to indemnify the Company's directors and
officers to the fullest extent permitted by the General Corporation Law of
Delaware. The Company believes that these provisions will assist the Company in
attracting and retaining qualified individuals to serve as directors.
 
                                       51
<PAGE>   53
 
                        SHARES ELIGIBLE FOR FUTURE SALE
 
   
     Prior to this offering, there has been no public market for the securities
of the Company. Upon completion of this offering, based upon the number of
shares outstanding at July 4, 1998, there will be 14,166,474 shares of Common
Stock of the Company outstanding (assuming no exercise of the Underwriters'
over-allotment option or outstanding options of the Company). Of these shares,
the 3,100,000 shares sold in this offering will be freely transferable without
restriction or further registration under the Securities Act, except that any
shares purchased by "affiliates" of the Company, as that term is defined in Rule
144 ("Rule 144") under the Securities Act ("Affiliates"), may generally only be
sold in compliance with the limitations of Rule 144 described below.
    
 
SALES OF RESTRICTED SECURITIES
 
   
     The remaining 11,066,474 outstanding shares of Common Stock are owned by
existing stockholders and are deemed "Restricted Shares" under Rule 144. These
shares may not be resold, except pursuant to an effective registration statement
or an applicable exemption from registration. Of these remaining shares,
approximately 79,000 shares of Common Stock will be eligible for sale under
Rules 144 and 701 on the ninety-first day after the effectiveness of this
offering. Stockholders of the Company, holding in the aggregate approximately
10,981,000 shares of Common Stock, have agreed to enter into the Lock-up
Agreements. At the end of the 180-day period, approximately 11,618,000 shares of
Common Stock (including approximately 551,000 shares of Common Stock which may
be acquired upon the exercise of outstanding options) will be eligible for sale
under Rules 144 and 701.
    
 
     In general, under Rule 144, as currently in effect, a person (or persons
whose shares are aggregated), including an Affiliate, who has beneficially owned
Restricted Shares for at least one year from the later of the date such
Restricted Shares were acquired from the Company and (if applicable) the date
they were acquired from an Affiliate, is entitled to sell, within any
three-month period, a number of shares that does not exceed the greater of 1% of
the then outstanding shares of Common Stock or the average weekly trading volume
in the public market during the four calendar weeks preceding such sale. Sales
under Rule 144 are also subject to certain requirements as to the manner and
notice of sale and the availability of public information concerning the
Company. All sales of shares of the Company's Common Stock, including Restricted
Shares, held by Affiliates of the Company must be sold under Rule 144, subject
to the foregoing volume limitations and other restrictions. In addition, under
Rule 144(k), if a period of at least two years has elapsed between the later of
the date restricted securities were acquired from the Company or (if applicable)
the date they were acquired from an Affiliate of the Company, a stockholder who
is not an Affiliate of the Company at the time of sale and has not been an
Affiliate with the Company for at least three months prior to the sale is
entitled to sell the shares immediately without compliance with the foregoing
requirements under Rule 144.
 
     The Company's directors and executive officers and certain of its
stockholders have agreed that they will not, without the prior written consent
of the representatives of the Underwriters, offer to sell, sell, contract to
sell, grant any option to sell or otherwise dispose of or require the Company to
file with the Commission a registration statement under the Securities Act to
register any shares of Common Stock or securities convertible or exchangeable
for shares of Common Stock or warrants or other rights to acquire shares of
Common Stock during the 180-day period following the effective date of the
Registration Statement of which this Prospectus is a part.
 
OPTIONS
 
   
     The Company plans to file registration statements under the Securities Act
to register an aggregate of approximately 4,000,000 shares of Common Stock
issuable under the 1991 Plan, the Incentive Plan, the Purchase Plan and the
Director Plan following the 180th day after the date of the Registration
Statement of which this Prospectus is a part. Upon registration, such shares
will be
    
 
                                       52
<PAGE>   54
 
eligible for immediate resale upon exercise, subject, in the case of Affiliates,
to the volume, manner of sale and notice requirements of Rule 144.
 
REGISTRATION RIGHTS
 
     Pursuant to the Third Amended and Restated Registration Rights Agreement
(the "Registration Rights Agreement"), dated as of February 13, 1998, among the
Company and certain persons and entities (the "Rightsholders"), the
Rightsholders will be entitled, following the offering, to certain rights with
respect to the registration under the Securities Act of a total of approximately
9,400,000 shares of Common Stock (the "Registrable Stock"). The Registration
Rights Agreement generally provides that, in the event the Company proposes to
register (the "Registration") any of its securities under the Securities Act,
the Rightsholders shall be entitled to include Registrable Stock in such
Registration, subject to the right of the managing underwriter of any
underwritten offering to limit for marketing reasons the number of shares of
Registrable Stock included in such "piggyback" registration period.
 
     The Rightsholders may, at any time after one year following the date of the
closing of this offering and upon the request of holders of not less than 35% of
the Registrable Stock then outstanding, require the Company to prepare and file
a registration statement under the Securities Act with respect to their shares
of Registrable Stock. The Company need effect only three such demand
registrations. In addition, at any time after the Company becomes eligible to
file a registration statement on Form S-3 (or any successor form), Rightsholders
may request the Company to effect a registration on Form S-3 of Registrable
Stock having an aggregate offering price of at least $250,000.
 
EFFECT OF SALES OF SHARES
 
     Prior to this offering, there has been no public market for the Common
Stock, and no prediction can be made as to the effect, if any, that market sales
of shares of Common Stock or the availability of shares for sale will have on
the market price of the Common Stock prevailing from time to time. Nevertheless,
sales of significant numbers of shares of the Common Stock in the public market
could adversely affect the market price of the Common Stock and could impair the
Company's future ability to raise capital through an offering of its equity
securities.
 
                                       53
<PAGE>   55
 
                                  UNDERWRITING
 
     Subject to the terms and conditions of the Underwriting Agreement, the
Underwriters named below (the "Underwriters") through their Representatives, BT
Alex. Brown Incorporated, Merrill Lynch, Pierce, Fenner & Smith Incorporated and
Piper Jaffray Inc. have severally agreed to purchase from the Company the
following respective numbers of shares of Common Stock at the initial public
offering price less the underwriting discounts and commissions set forth on the
cover page of this Prospectus:
 
   
<TABLE>
<CAPTION>
                                                                 NUMBER
                                                                   OF
UNDERWRITER                                                      SHARES
- -----------                                                     ---------
<S>                                                             <C>
BT Alex. Brown Incorporated.................................
Merrill Lynch, Pierce, Fenner & Smith
             Incorporated...................................
Piper Jaffray Inc...........................................
                                                                ---------
          Total.............................................    3,100,000
                                                                =========
</TABLE>
    
 
     The Underwriting Agreement provides that the obligations of the
Underwriters are subject to certain conditions precedent and that the
Underwriters will purchase all shares of the Common Stock offered hereby if any
of such shares are purchased.
 
     The Company has been advised by the Representatives of the Underwriters
that the Underwriters propose to offer the shares of Common Stock to the public
at the initial public offering price set forth on the cover page of this
Prospectus, and to certain dealers at such price less a concession not in excess
of $     per share. The Underwriters may allow, and such dealers may reallow, a
concession not in excess of $     per share to certain other dealers. After the
initial public offering, the public offering price and other selling terms may
be changed by the Representatives of the Underwriters.
 
   
     The Company has granted to the Underwriters an option, exercisable not
later than 30 days after the date of this Prospectus, to purchase up to 465,000
additional shares of Common Stock at the initial public offering price less the
underwriting discounts and commissions set forth on the cover page of this
Prospectus. To the extent that the Underwriters exercise such option, each of
the Underwriters will have a firm commitment to purchase approximately the same
percentage thereof that the number of shares of Common Stock to be purchased by
it shown in the above table bears to 3,100,000, and the Company will be
obligated, pursuant to the option, to sell such shares to the Underwriters. The
Underwriters may exercise such option only to cover over-allotments made in
connection with the sale of the Common Stock offered hereby. If purchased, the
Underwriters will offer such additional shares on the same terms as those on
which the 3,100,000 shares are being offered.
    
 
     The Company has agreed to indemnify the Underwriters and their controlling
persons against certain liabilities under the Securities Act.
 
     The Representatives of the Underwriters have advised the Company that the
Underwriters do not intend to confirm sales to any accounts over which they
exercise discretionary authority.
 
     In connection with this offering, the Underwriters and certain other
persons participating in this offering may purchase and sell the Common Stock in
the open market in accordance with Regulation M under the Securities Exchange
Act of 1934, as amended. These transactions may include over-allotment and
stabilizing transactions and purchases to cover syndicate short positions
created in connection with the offering. Stabilizing transactions consist of
certain bids or purchases for the purpose of preventing or retarding a decline
in the market price of the Common Stock; and syndicate short positions involve
the sale by the Underwriters of a greater number of shares of Common Stock than
they are required to purchase from the Company in the offering. The
 
                                       54
<PAGE>   56
 
Underwriters also may impose a penalty bid, whereby selling concessions allowed
to syndicate members or other broker-dealers in respect of the securities sold
in the offering for their account may be reclaimed by the syndicate if such
securities are repurchased by the syndicate in stabilizing or covering
transactions. These activities may stabilize, maintain or otherwise affect the
market price of the Common Stock, and as a result, such price may be higher than
the price that might otherwise prevail in the open market. The Underwriters and
such other persons are not required to engage in these activities, and may end
any of these activities at any time. These transactions may be effected on the
Nasdaq National Market, in the over-the-counter market or otherwise.
 
     Prior to this offering, there has been no public market for the Common
Stock of the Company. Consequently, the initial public offering price for the
Common Stock will be determined by negotiations among the Company and the
Representatives of the Underwriters. Among the factors to be considered in such
negotiations will be prevailing market conditions, the results of operations of
the Company in recent periods, the market capitalizations and stages of
development of other companies which the Company and the Representatives of the
Underwriters believe to be comparable to the Company, estimates of the business
potential of the Company, the present state of the Company's development and
other factors deemed relevant. Application has been made for quotation of the
Common Stock on the Nasdaq National Market under the symbol "ASPM."
 
                                 LEGAL MATTERS
 
     The validity of the shares of Common Stock offered by the Company hereby
will be passed upon for the Company by Hale and Dorr LLP, Boston, Massachusetts,
and for the Underwriters by Testa, Hurwitz & Thibeault, LLP, Boston,
Massachusetts. An investment partnership comprised of certain partners of Hale
and Dorr LLP owns an aggregate of 9,107 shares of Common Stock of the Company.
 
                                    EXPERTS
 
     The audited financial statements as of December 31, 1996 and 1997 and for
the years then ended have been audited by Arthur Andersen LLP, independent
public accountants, as indicated in their report with respect thereto, and are
included herein in reliance upon the authority of said firm as experts in giving
said report.
 
   
     The Company's financial statements for the year ended December 31, 1995
included in this Prospectus have been so included in reliance on the report of
PricewaterhouseCoopers LLP, independent accountants, given on the authority of
said firm as experts in auditing and accounting.
    
 
                             ADDITIONAL INFORMATION
 
     The Company has filed with the Securities and Exchange Commission (the
"Commission") a Registration Statement (which term shall include all amendments,
exhibits, schedules and supplements thereto) on Form S-1 under the Securities
Act with respect to the shares of Common Stock offered hereby. This Prospectus,
which constitutes a part of the Registration Statement, does not contain all of
the information set forth in the Registration Statement, certain parts of which
are omitted in accordance with the rules and regulations of the Commission, to
which Registration Statement reference is hereby made. Statements made in this
Prospectus as to the contents of any contract, agreement or other document
referred to are not necessarily complete. With respect to each such contract,
agreement or other document filed as an exhibit to the Registration Statement,
reference is made to the exhibit for a more complete description of the matter
involved, and each such statement shall be deemed qualified in its entirety by
such reference. The Registration Statement and the exhibits thereto may be
inspected and copied at prescribed rates at the public reference facilities
maintained by the Commission at Room 1024, Judiciary Plaza, 450 Fifth Street,
N.W., Washington, D.C. 20549 and at the regional offices of the Commission
located at Seven World Trade Center, 13th Floor, New York, New York 10048 and
Citicorp Center, 500 West Madison Street,
                                       55
<PAGE>   57
 
Suite 1400, Chicago, Illinois 60661. In addition, the Company is required to
file electronic versions to these documents with the Commission through the
Commission's Electronic Data Gathering, Analysis, and Retrieval (EDGAR) system.
The Commission maintains a World Wide Web site at http://www.sec.gov that
contains reports, proxy and information statements and other information
regarding registrants that file electronically with the Commission.
 
     The Company intends to distribute to its stockholders annual reports
containing audited consolidated financial statements. The Company also intends
to make available to its stockholders, within 45 days after the end of each
fiscal quarter, reports for the first three quarters of each fiscal year
containing interim unaudited financial information.
 
                                       56
<PAGE>   58
 
                          ASPECT MEDICAL SYSTEMS, INC.
 
                         INDEX TO FINANCIAL STATEMENTS
 
   
<TABLE>
<S>                                                             <C>
Report of Arthur Andersen LLP, Independent Public
  Accountants...............................................    F-2
Report of Price Waterhouse LLP, Independent Accountants.....    F-3
Balance Sheets as of December 31, 1996 and 1997, July 4,
  1998 (Unaudited) and Pro Forma July 4, 1998 (Unaudited)...    F-4
Statements of Operations for the Years Ended December 31,
  1995, 1996, and 1997 and for the Six Months Ended June 28,
  1997 (Unaudited) and July 4, 1998 (Unaudited).............    F-5
Statements of Stockholders' Equity for the Years Ended
  December 31, 1995, 1996 and 1997 and for the Six Months
  Ended July 4, 1998 (Unaudited)............................    F-6
Statements of Cash Flows for the Years Ended December 31,
  1995, 1996, and 1997 and for the Six Months Ended June 28,
  1997 (Unaudited) and July 4, 1998 (Unaudited).............    F-7
Notes to Financial Statements...............................    F-8
</TABLE>
    
 
                                       F-1
<PAGE>   59
 
                    REPORT OF INDEPENDENT PUBLIC ACCOUNTANTS
 
To Aspect Medical Systems, Inc.:
 
     We have audited the accompanying balance sheets of Aspect Medical Systems,
Inc. (a Delaware corporation) as of December 31, 1996 and 1997, and the related
statements of operations, stockholders' equity and cash flows for the years then
ended. These financial statements are the responsibility of the Company's
management. Our responsibility is to express an opinion on these financial
statements based on our audits.
 
     We conducted our audits in accordance with generally accepted auditing
standards. Those standards require that we plan and perform the audit to obtain
reasonable assurance about whether the financial statements are free of material
misstatement. An audit includes examining, on a test basis, evidence supporting
the amounts and disclosures in the financial statements. An audit also includes
assessing the accounting principles used and significant estimates made by
management, as well as evaluating the overall financial statement presentation.
We believe that our audits provide a reasonable basis for our opinion.
 
     In our opinion, the financial statements referred to above present fairly,
in all material respects, the financial position of Aspect Medical Systems, Inc.
as of December 31, 1996 and 1997, and the results of its operations and cash
flows for the years then ended, in conformity with generally accepted accounting
principles.
 
                                          /s/  Arthur Andersen LLP
 
Boston, Massachusetts
March 27, 1998
 
                                       F-2
<PAGE>   60
 
                       REPORT OF INDEPENDENT ACCOUNTANTS
 
To the Board of Directors and Stockholders
of Aspect Medical Systems, Inc.
 
     In our opinion, the accompanying statements of operations, of stockholders'
equity and of cash flows present fairly, in all material respects, the results
of operations and cash flows of Aspect Medical Systems, Inc. for the year ended
December 31, 1995, in conformity with generally accepted accounting principles.
These financial statements are the responsibility of the Company's management;
our responsibility is to express an opinion on these financial statements based
on our audit. We conducted our audit of these statements in accordance with
generally accepted auditing standards which require that we plan and perform the
audit to obtain reasonable assurance about whether the financial statements are
free of material misstatement. An audit includes examining, on a test basis,
evidence supporting the amounts and disclosures in the financial statements,
assessing the accounting principles used and significant estimates made by
management, and evaluating the overall financial statement presentation. We
believe that our audit provides a reasonable basis for the opinion expressed
above. We have not audited the financial statements of the Company for any
period subsequent to December 31, 1995.
 
/s/  PRICE WATERHOUSE LLP
 
Boston, Massachusetts
July 3, 1996
 
                                       F-3
<PAGE>   61
 
                          ASPECT MEDICAL SYSTEMS, INC.
 
                                 BALANCE SHEETS
 
   
<TABLE>
<CAPTION>
                                                                                                    PRO FORMA
                                                   DECEMBER 31,    DECEMBER 31,      JULY 4,       JULY 4, 1998
                                                       1996            1997            1998          (NOTE 2)
                                                   ------------    ------------    ------------    ------------
                                                                                   (UNAUDITED)     (UNAUDITED)
<S>                                                <C>             <C>             <C>             <C>
ASSETS
Current assets:
  Cash and cash equivalents......................  $  1,353,920    $    368,507    $  3,300,024    $  3,300,024
  Marketable securities..........................       876,741       4,612,462       6,830,863       6,830,863
  Accounts receivable, net of allowance of
    $50,000, $62,400 and $102,310 at December 31,
    1996, 1997 and July 4, 1998, respectively....       152,440         719,172       1,306,003       1,306,003
  Investment in sales-type leases................        44,676         136,392         531,556         531,556
  Inventory......................................     1,099,837         387,479         951,129         951,129
  Other current assets...........................       137,619         245,962         367,861         367,861
                                                   ------------    ------------    ------------    ------------
         Total current assets....................     3,665,233       6,469,974      13,287,436      13,287,436
Property and equipment, net......................       208,984         923,559       1,896,835       1,896,835
Investment in sales-type leases..................        98,864         209,074         902,213         902,213
Other long-term assets...........................            --              --          38,956          38,956
                                                   ------------    ------------    ------------    ------------
         Total assets............................  $  3,973,081    $  7,602,607    $ 16,125,440    $ 16,125,440
                                                   ============    ============    ============    ============
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities:
  Current portion of long-term debt (Note 18)....  $    429,871    $    154,906    $    291,945    $    291,945
  Accounts payable...............................       659,277       1,119,055       1,222,842       1,222,842
  Accrued liabilities............................       724,331       1,500,591       2,933,754       2,933,754
  Deferred revenue...............................       823,000         643,000       1,695,830       1,695,830
                                                   ------------    ------------    ------------    ------------
         Total current liabilities...............     2,636,479       3,417,552       6,144,371       6,144,371
                                                   ------------    ------------    ------------    ------------
Long-term debt (Note 18).........................       270,273         117,680         681,926         681,926
                                                   ------------    ------------    ------------    ------------
Commitments and contingencies (Note 13)
Stockholders' equity:
  Preferred Stock, $.01 par value; (pro forma --
    5,000,000 shares authorized, no shares issued
    or outstanding)..............................            --              --              --              --
  Convertible Preferred Stock, $.01 par value;
    18,843,224 shares authorized, 4,207,326,
    7,647,275 and 9,313,509 shares issued and
    outstanding at December 31, 1996 and 1997 and
    July 4, 1998, respectively (liquidation
    preference -- $41,425,301 at July 4, 1998)
    (pro forma -- no shares authorized, issued or
    outstanding).................................    25,891,270      38,726,070      50,299,886              --
  Common Stock, $.01 par value; 14,500,000 shares
    authorized, 93,424, 1,548,027 and 1,752,965
    shares issued and outstanding at December 31,
    1996 and 1997, and July 4, 1998, respectively
    (pro forma -- 40,000,000 shares authorized,
    11,066,474 shares issued and outstanding)....           934          15,480          17,530         110,665
  Additional paid-in capital.....................        31,096         338,970       1,369,598      51,576,349
  Notes receivable from employees and
    directors....................................            --        (273,579)       (306,182)       (306,182)
  Deferred compensation..........................            --              --        (825,350)       (825,350)
  Unrealized gain (loss) on marketable
    securities...................................          (162)          3,098           3,393           3,393
  Accumulated deficit............................   (24,856,809)    (34,742,664)    (41,259,732)    (41,259,732)
                                                   ------------    ------------    ------------    ------------
         Total stockholders' equity..............     1,066,329       4,067,375       9,299,143       9,299,143
                                                   ------------    ------------    ------------    ------------
         Total liabilities and stockholders'
           equity................................  $  3,973,081    $  7,602,607    $ 16,125,440    $ 16,125,440
                                                   ============    ============    ============    ============
</TABLE>
    
 
   The accompanying notes are an integral part of these financial statements.
                                       F-4
<PAGE>   62
 
                          ASPECT MEDICAL SYSTEMS, INC.
 
                            STATEMENTS OF OPERATIONS
 
   
<TABLE>
<CAPTION>
                                                   YEAR ENDED DECEMBER 31,                SIX MONTHS ENDED
                                           ----------------------------------------   -------------------------
                                                                                       JUNE 28,       JULY 4,
                                              1995          1996           1997          1997          1998
                                           -----------   -----------   ------------   -----------   -----------
                                                                                      (UNAUDITED)   (UNAUDITED)
<S>                                        <C>           <C>           <C>            <C>           <C>
Revenue..................................  $ 1,067,207   $ 1,388,788   $  3,067,573   $ 1,075,807   $ 4,420,165
Costs and expenses:
  Costs of revenue.......................      704,386     1,095,872      3,601,569     1,380,972     2,662,249
  Research and development...............    2,870,231     2,338,239      2,603,117     1,434,419     1,941,915
  Sales and marketing....................    1,284,880     1,560,635      4,813,505     1,721,239     4,669,543
  General and administrative.............    1,814,850     1,871,071      2,357,695     1,193,788     1,960,271
                                           -----------   -----------   ------------   -----------   -----------
         Total costs and expenses........    6,674,347     6,865,817     13,375,886     5,730,418    11,233,978
                                           -----------   -----------   ------------   -----------   -----------
Loss from operations.....................   (5,607,140)   (5,477,029)   (10,308,313)   (4,654,611)   (6,813,813)
Interest income..........................      145,636       143,675        500,485       246,057       312,857
Interest expense.........................      (84,405)      (63,084)       (78,027)      (38,853)      (16,112)
                                           -----------   -----------   ------------   -----------   -----------
Net loss.................................  $(5,545,909)  $(5,396,438)  $ (9,885,855)  $(4,447,407)  $(6,517,068)
                                           ===========   ===========   ============   ===========   ===========
Net loss per share:
  Basic and diluted......................     $(281.65)      $(57.76)       $(16.23)      $(10.88)       $(6.34)
                                           ===========   ===========   ============   ===========   ===========
  Pro forma basic and diluted............                                    $(1.28)                     $(0.65)
                                                                       ============                 ===========
Shares used in computing net loss per
  share:
  Basic and diluted......................       19,691        93,424        609,026       408,956     1,027,166
  Pro forma basic and diluted............                                 7,707,188                   9,951,283
</TABLE>
    
 
   The accompanying notes are an integral part of these financial statements.
                                       F-5
<PAGE>   63
 
                          ASPECT MEDICAL SYSTEMS, INC.
 
                       STATEMENTS OF STOCKHOLDERS' EQUITY
   
<TABLE>
<CAPTION>
                                                                COMMON STOCK                        NOTES
                                    CONVERTIBLE PREFERRED    -------------------                 RECEIVABLE
                                            STOCK                                  ADDITIONAL       FROM
                                   -----------------------                 PAR      PAID-IN       EMPLOYEES       DEFERRED
                                    SHARES       AMOUNT       SHARES      VALUE     CAPITAL     AND DIRECTORS   COMPENSATION
                                   ---------   -----------   ---------   -------   ----------   -------------   ------------
<S>                                <C>         <C>           <C>         <C>       <C>          <C>             <C>
Balance, December 31, 1994.......     49,137   $18,384,462       5,306   $    53   $   11,205     $      --      $      --
 Issuance of common stock........         --            --      87,952       879       16,691            --             --
 Issuance of Series B-1
   convertible preferred stock,
   net of issuance costs of
   approximately $80,000.........  2,075,042     4,069,909          --        --           --            --             --
 Issuance of anti-dilution
   shares........................    357,761            --          --        --           --            --             --
 Issuance of common stock upon
   exercise of common stock
   options.......................         --            --         166         2        3,200            --             --
 Change in unrealized gain (loss)
   on marketable securities......         --            --          --        --           --            --             --
 Net loss........................         --            --          --        --           --            --             --
                                   ---------   -----------   ---------   -------   ----------     ---------      ---------
Balance, December 31, 1995.......  2,481,940    22,454,371      93,424       934       31,096            --             --
 Issuance of Series B-1
   convertible preferred stock,
   net of issuance costs of
   approximately $14,000.........  1,725,386     3,436,899          --        --           --            --             --
 Change in unrealized gain (loss)
   on marketable securities......         --            --          --        --           --            --             --
 Net loss........................         --            --          --        --           --            --             --
                                   ---------   -----------   ---------   -------   ----------     ---------      ---------
Balance, December 31, 1996.......  4,207,326    25,891,270      93,424       934       31,096            --             --
 Issuance of Series C convertible
   preferred stock, net of
   issuance costs of
   approximately $61,000.........  3,439,949    12,834,800          --        --           --            --             --
 Issuance of common stock upon
   exercise of common stock
   options.......................         --            --   1,454,603    14,546      307,874      (273,579)            --
 Change in unrealized gain (loss)
   on marketable securities......         --            --          --        --           --            --             --
 Net loss........................         --            --          --        --           --            --             --
                                   ---------   -----------   ---------   -------   ----------     ---------      ---------
Balance, December 31, 1997.......  7,647,275    38,726,070   1,548,027    15,480      338,970      (273,579)            --
 Issuance of Series D convertible
   preferred stock, net of
   issuance costs of
   approximately $73,000
   (unaudited)...................  1,666,234    11,573,816          --        --           --            --             --
 Issuance of common stock upon
   exercise of common stock
   options(unaudited)............         --            --     204,938     2,050      140,973       (63,000)            --
 Payments on notes receivable
   from employees and directors
   (unaudited)...................         --            --          --        --           --        30,397             --
 Deferred compensation related to
   stock options (unaudited).....         --            --          --        --      889,655            --       (889,655)
 Amortization of deferred
   compensation related to stock
   options (unaudited)...........         --            --          --        --           --            --         64,305
 Change in unrealized gain (loss)
   on marketable
   securities(unaudited).........         --            --          --        --           --            --             --
 Net loss(unaudited).............         --            --          --        --           --            --             --
                                   ---------   -----------   ---------   -------   ----------     ---------      ---------
Balance, July 4, 1998
 (unaudited).....................  9,313,509   $50,299,886   1,752,965   $17,530   $1,369,598     $(306,182)     $(825,350)
                                   =========   ===========   =========   =======   ==========     =========      =========
 
<CAPTION>
 
                                     UNREALIZED
                                   GAIN (LOSS) ON                      TOTAL
                                     MARKETABLE     ACCUMULATED    STOCKHOLDERS'
                                     SECURITIES       DEFICIT         EQUITY
                                   --------------   ------------   -------------
<S>                                <C>              <C>            <C>
Balance, December 31, 1994.......     $(21,561)     $(13,914,462)   $ 4,459,697
 Issuance of common stock........           --                --         17,570
 Issuance of Series B-1
   convertible preferred stock,
   net of issuance costs of
   approximately $80,000.........           --                --      4,069,909
 Issuance of anti-dilution
   shares........................           --                --             --
 Issuance of common stock upon
   exercise of common stock
   options.......................           --                --          3,202
 Change in unrealized gain (loss)
   on marketable securities......       23,905                --         23,905
 Net loss........................           --        (5,545,909)    (5,545,909)
                                      --------      ------------    -----------
Balance, December 31, 1995.......        2,344       (19,460,371)     3,028,374
 Issuance of Series B-1
   convertible preferred stock,
   net of issuance costs of
   approximately $14,000.........           --                --      3,436,899
 Change in unrealized gain (loss)
   on marketable securities......       (2,506)               --         (2,506)
 Net loss........................           --        (5,396,438)    (5,396,438)
                                      --------      ------------    -----------
Balance, December 31, 1996.......         (162)      (24,856,809)     1,066,329
 Issuance of Series C convertible
   preferred stock, net of
   issuance costs of
   approximately $61,000.........           --                --     12,834,800
 Issuance of common stock upon
   exercise of common stock
   options.......................           --                --         48,841
 Change in unrealized gain (loss)
   on marketable securities......        3,260                --          3,260
 Net loss........................           --        (9,885,855)    (9,885,855)
                                      --------      ------------    -----------
Balance, December 31, 1997.......        3,098       (34,742,664)     4,067,375
 Issuance of Series D convertible
   preferred stock, net of
   issuance costs of
   approximately $73,000
   (unaudited)...................           --                --     11,573,816
 Issuance of common stock upon
   exercise of common stock
   options(unaudited)............           --                --         80,023
 Payments on notes receivable
   from employees and directors
   (unaudited)...................           --                --         30,397
 Deferred compensation related to
   stock options (unaudited).....           --                --             --
 Amortization of deferred
   compensation related to stock
   options (unaudited)...........           --                --         64,305
 Change in unrealized gain (loss)
   on marketable
   securities(unaudited).........          295                --            295
 Net loss(unaudited).............           --        (6,517,068)    (6,517,068)
                                      --------      ------------    -----------
Balance, July 4, 1998
 (unaudited).....................     $  3,393      $(41,259,732)   $ 9,299,143
                                      ========      ============    ===========
</TABLE>
    
 
   The accompanying notes are an integral part of these financial statements.
                                       F-6
<PAGE>   64
 
                          ASPECT MEDICAL SYSTEMS, INC.
 
                            STATEMENTS OF CASH FLOWS
 
   
<TABLE>
<CAPTION>
                                                    YEAR ENDED DECEMBER 31,                SIX MONTHS ENDED
                                            ---------------------------------------   ---------------------------
                                                                                        JUNE 28,       JULY 4,
                                               1995          1996          1997           1997           1998
                                            -----------   -----------   -----------   ------------   ------------
                                                                                      (UNAUDITED)    (UNAUDITED)
<S>                                         <C>           <C>           <C>           <C>            <C>
Cash flows from operating activities:
  Net loss................................  $(5,545,909)  $(5,396,438)  $(9,885,855)  $ (4,447,407)  $ (6,517,068)
  Adjustments to reconcile net loss to net
    cash used for operating activities --
    Depreciation and amortization.........      575,373       189,378       192,571         95,313        160,474
    Provision for doubtful accounts.......           --        43,000        14,333             --         40,000
    Amortization of deferred
      compensation........................           --            --            --             --         64,305
    Changes in assets and liabilities --
      Increase in accounts receivable.....     (188,004)      (92,990)     (437,525)       (67,513)      (626,831)
      (Increase) decrease in inventory....         (214)       61,193       763,483        (64,045)      (563,650)
      Decrease (increase) in other current
        assets............................      121,764       (60,628)     (108,343)      (163,322)      (121,899)
      Increase in investment in sales-type
        leases............................           --            --      (345,466)       (88,306)    (1,088,303)
      Increase in other long-term
        assets............................           --            --            --             --        (38,956)
      (Decrease) increase in accounts
        payable...........................     (100,281)      493,575       459,778       (180,447)       103,787
      Increase (decrease) in accrued
        liabilities.......................      454,407        (4,385)      776,260        633,878      1,433,163
      (Decrease) increase in deferred
        revenue...........................     (121,717)      814,717      (180,000)       136,249      1,052,830
                                            -----------   -----------   -----------   ------------   ------------
        Net cash used for operating
          activities......................   (4,804,581)   (3,952,578)   (8,750,764)    (4,145,600)    (6,102,148)
                                            -----------   -----------   -----------   ------------   ------------
Cash flows from investing activities:
  Acquisition of property and equipment...     (272,270)     (622,384)     (958,271)      (121,318)    (1,133,750)
  Purchases of marketable securities......     (347,820)  (23,953,144)  (65,379,625)   (39,186,351)   (38,316,566)
  Proceeds from sales of marketable
    securities............................    2,800,052    24,045,377    61,647,164     33,021,116     36,098,460
                                            -----------   -----------   -----------   ------------   ------------
        Net cash provided by (used for)
          investing activities............    2,179,962      (530,151)   (4,690,732)    (6,286,553)    (3,351,856)
                                            -----------   -----------   -----------   ------------   ------------
Cash flows from financing activities:
  Principal payments on capital lease
    obligations...........................     (206,646)     (287,616)     (427,558)      (194,265)       (74,546)
  Proceeds from sale leaseback of property
    and equipment.........................      238,996       330,291            --             --             --
  Proceeds from equipment loan............           --            --            --             --        775,831
  Proceeds received from issuance of
    convertible notes.....................      500,000            --            --             --             --
  Proceeds from issuance of convertible
    preferred stock, net of stock issuance
    costs.................................    3,569,909     3,436,899    12,834,800     12,684,800     11,573,816
  Proceeds from issuance of common
    stock.................................       20,772            --        48,841         48,061         80,023
  Payments received on notes receivable
    from employees and directors..........           --            --            --             --         30,397
                                            -----------   -----------   -----------   ------------   ------------
        Net cash provided by financing
          activities......................    4,123,031     3,479,574    12,456,083     12,538,596     12,385,521
                                            -----------   -----------   -----------   ------------   ------------
Net increase (decrease) in cash and cash
  equivalents.............................    1,498,412    (1,003,155)     (985,413)     2,106,443      2,931,517
Cash and cash equivalents, beginning of
  period..................................      858,663     2,357,075     1,353,920      1,353,920        368,507
                                            -----------   -----------   -----------   ------------   ------------
Cash and cash equivalents, end of
  period..................................  $ 2,357,075   $ 1,353,920   $   368,507   $  3,460,363   $  3,300,024
                                            ===========   ===========   ===========   ============   ============
Supplemental disclosure of cash flow
  information:
  Interest paid...........................  $   209,404   $    59,000   $    78,000   $     39,000   $     16,000
                                            ===========   ===========   ===========   ============   ============
Supplemental disclosure of noncash
  financing activities:
  Capital lease obligations totaling
    $239,000 and $367,000, including sale
    leaseback transactions, were incurred
    during 1995 and 1996, respectively.
  Convertible notes totaling $500,000 were
    converted into 250,000 shares of
    Series B-1 convertible preferred stock
    in 1995.
</TABLE>
    
 
   The accompanying notes are an integral part of these financial statements.
                                       F-7
<PAGE>   65
 
                          ASPECT MEDICAL SYSTEMS, INC.
 
                         NOTES TO FINANCIAL STATEMENTS
                (INCLUDING DATA APPLICABLE TO UNAUDITED PERIODS)
 
(1)  DESCRIPTION OF OPERATIONS
 
   
     Aspect Medical Systems, Inc. (the "Company") develops, manufactures and
markets anesthesia monitoring systems that enable anesthesia providers to assess
levels of consciousness and administer the appropriate amount of anesthetics
during surgery. The BIS System incorporates the Company's proprietary disposable
BIS Sensors and the A-2000 BIS Monitor, which was cleared for marketing by the
United States Food and Drug Administration (the "FDA") in February 1998. The BIS
System is based on Aspect's patented core technology, the Bispectral Index (the
"BIS index"), which is the only FDA cleared, commercially available direct
measure of the effects of anesthetics on the brain.
    
 
   
     The Company incurred net losses of $5,545,909, $5,396,438 and $9,885,855
for the years ended December 31, 1995, 1996 and 1997, respectively, and at July
4, 1998 had an accumulated deficit of $41,259,732. Principal risks that may
affect the business, results of operations and financial condition of the
Company include market acceptance of the Company's technology and products,
limited sales and marketing experience, the reliance on a single product family,
manufacturing risks, the dependence on single source or limited suppliers,
technological risks and other risks.
    
 
(2)  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
 
     A summary of the significant accounting policies used by the Company in the
preparation of its financial statements are as follows:
 
  Interim Financial Statements
 
   
     The accompanying balance sheet as of July 4, 1998, statements of operations
and cash flows for the six months ended June 28, 1997 and July 4, 1998 and the
statement of stockholders' equity for the six months ended July 4, 1998 are
unaudited but, in the opinion of management, include all adjustments (consisting
of normal, recurring adjustments) necessary for a fair presentation for results
of these interim periods. The results of operations for the six months ended
July 4, 1998 are not necessarily indicative of results to be expected for the
entire year or for any other interim period.
    
 
   
     The Company follows a system of fiscal months as opposed to calendar
months. Under this system, the first eleven months of each fiscal year end on a
Saturday and the last month of the fiscal year always ends on December 31. All
references to the six months ended June 28, 1997 relate to the period from
January 1, 1997 to June 28, 1997, and all references to the six months ended
July 4, 1998 relate to the period from January 1, 1998 to July 4, 1998.
    
 
  Unaudited Pro Forma Presentation
 
   
     Under the terms of the Company's agreements with the holders of the
convertible preferred stock, all of such preferred stock will be converted
automatically into shares of common stock upon the closing of the Company's
initial public offering. The unaudited pro forma balance sheet information at
July 4, 1998 reflects the conversion of all series of preferred stock into
9,313,509 shares of common stock as if the conversion occurred on July 4, 1998.
    
 
  Cash, Cash Equivalents and Marketable Securities
 
     The Company invests its excess cash in money market accounts, U.S. Treasury
bills, high grade commercial paper, and debt obligations of various government
agencies. The Company considers all highly liquid debt instruments purchased
with an original maturity of three months or less to be cash equivalents.
 
                                       F-8
<PAGE>   66
                          ASPECT MEDICAL SYSTEMS, INC.
 
                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)
                (INCLUDING DATA APPLICABLE TO UNAUDITED PERIODS)
 
     The Company accounts for its investments in accordance with Statement of
Financial Accounting Standards (SFAS) No. 115, Accounting for Certain
Investments in Debt and Equity Securities. In accordance with SFAS No. 115, the
Company has classified all of its investments as available-for-sale at December
31, 1996 and 1997, respectively. The securities are reported at fair value, with
unrealized gains and losses excluded from earnings and reported as a separate
component of stockholders' equity.
 
  Revenue Recognition
 
     Revenue from equipment sales, disposable product sales and sales-type
leases are recognized at the time of shipment. Payments received prior to
shipment are recorded as deferred revenue. The Company has entered into certain
licensing and distribution agreements for which payments received in advance are
recorded as deferred revenue. Revenue is recognized as earned per the terms of
the respective agreements. The Company provides for the cost of warranty at the
time of product shipment.
 
  Inventory
 
     Inventory is valued at the lower of cost or estimated market, cost being
determined on a first-in, first-out basis.
 
  Property and Equipment
 
     Property and equipment is recorded at cost and depreciated using the
straight-line method over the estimated useful lives of the related equipment.
Equipment held under capital leases is stated at the lower of the fair market
value of the equipment or the present value of the minimum lease payments at the
inception of the lease and is amortized on a straight-line basis over the
shorter of the lives of the related assets or the term of the leases.
Maintenance and repair expenditures are charged to expense as incurred.
 
  Income Taxes
 
     The Company accounts for income taxes in accordance with SFAS No. 109,
Accounting for Income Taxes. Under this method, deferred tax assets and
liabilities are recognized for the expected future tax consequences, utilizing
currently enacted tax rates, of temporary differences between the carrying
amounts and the tax bases of assets and liabilities. Deferred tax assets are
recognized, net of any valuation allowance, for the estimated future tax effects
of deductible temporary differences and tax operating loss and credit
carryforwards.
 
  Concentration of Credit Risk, Significant Customer and Single or Limited
Source Suppliers
 
     Financial instruments that potentially expose the Company to concentrations
of credit risk consist primarily of trade accounts receivable, investment in
sales-type lease receivables and investments. To minimize the risk with respect
to accounts receivable and investment in sales-type lease receivables, the
Company maintains reserves for potential credit losses and such losses, in the
aggregate, have not exceeded management's expectations. The Company maintains
cash, cash equivalents and investments with various financial institutions. The
Company performs periodic evaluations of the relative credit quality of
investments and Company policy is designed to limit exposure to any one
institution or type of investment. The primary objective of the Company's
investment strategy is the safety of the principal invested.
 
                                       F-9
<PAGE>   67
                          ASPECT MEDICAL SYSTEMS, INC.
 
                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)
                (INCLUDING DATA APPLICABLE TO UNAUDITED PERIODS)
 
   
     At December 31, 1996 and 1997 and July 4, 1998, accounts receivable from
one of the Company's international distributors accounted for approximately 8%,
19% and 23%, respectively, of the total amounts due to the Company. For the
years ended December 31, 1995, 1996 and 1997, sales to this customer accounted
for approximately 47%, 49% and 35%, respectively, of the Company's total
revenue. For the six months ended July 4, 1998, sales to this customer accounted
for approximately 17% of total revenue. Effective July 1, 1998, this customer no
longer distributes the Company's monitors.
    
 
     The Company currently obtains certain key components of its products from
single or limited sources. The Company purchases components pursuant to purchase
orders rather than long-term supply agreements. The Company has experienced
shortages and delays in obtaining certain components of its products in the
past. There can be no assurance that the Company will not experience similar
delays or shortages in the future. The disruption or termination of the supply
of components or a significant increase in the costs of these components from
these sources could have a material adverse effect on the Company's business,
financial condition and results of operations.
 
  Comprehensive Income
 
     In June 1997, the FASB issued SFAS No. 130, Reporting Comprehensive Income.
SFAS No. 130 requires disclosure of all components of comprehensive income on an
annual and interim basis. Comprehensive income is defined as the change in
equity of a business enterprise during a period from transactions and other
events and circumstances from non-owner sources. SFAS No. 130 is effective for
fiscal years beginning after December 15, 1997. The adoption of SFAS No. 130 did
not have a material effect on the Company's financial statements, as the only
element of comprehensive income impacting the Company is the unrealized gain
(loss) on marketable securities.
 
  Use of Estimates
 
     The preparation of financial statements in conformity with generally
accepted accounting principles requires management to make estimates and
assumptions that affect the reported amounts of assets and liabilities and
disclosure of contingent assets and liabilities at the date of the financial
statements and the reported amounts of revenues and expenses during the
reporting period. Actual results could differ from those estimates.
 
  Fair Value of Financial Instruments
 
     The estimated fair market values of the Company's financial instruments,
which include marketable securities, accounts receivable, investment in
sales-type leases, accounts payable and capital lease obligations, approximate
their carrying values.
 
                                      F-10
<PAGE>   68
                          ASPECT MEDICAL SYSTEMS, INC.
 
                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)
                (INCLUDING DATA APPLICABLE TO UNAUDITED PERIODS)
 
(3)  CASH EQUIVALENTS AND MARKETABLE SECURITIES
 
     Cash and cash equivalents consist of the following:
 
   
<TABLE>
<CAPTION>
                                                    DECEMBER 31,
                                               ----------------------      JULY 4,
                                                  1996         1997         1998
                                               ----------    --------    -----------
                                                                         (UNAUDITED)
<S>                                            <C>           <C>         <C>
Cash.........................................  $  369,566    $131,757    $1,071,652
U.S. Government debt securities..............     280,036     236,750       481,962
Corporate debt securities....................     704,318          --     1,746,410
                                               ----------    --------    ----------
                                               $1,353,920    $368,507    $3,300,024
                                               ==========    ========    ==========
</TABLE>
    
 
   
     Available-for-sale securities included in marketable securities at December
31, 1996 and 1997 and July 4, 1998 consist of the following:
    
 
   
<TABLE>
<CAPTION>
                                          AMORTIZED     UNREALIZED    UNREALIZED       FAIR
                                             COST         GAINS         LOSSES        VALUE
                                          ----------    ----------    ----------    ----------
<S>                                       <C>           <C>           <C>           <C>
December 31, 1996 --
  U.S. Government debt securities.......  $  220,929      $   --        $  --       $  220,929
  Corporate debt securities.............     405,974          --         (162)         405,812
  Municipal notes.......................     250,000          --           --          250,000
                                          ----------      ------        -----       ----------
                                          $  876,903      $   --        $(162)      $  876,741
                                          ==========      ======        =====       ==========
December 31, 1997 --
  U.S. Government debt securities.......  $   99,187      $   --        $  --       $   99,187
  Corporate debt securities.............   4,010,177       3,098           --        4,013,275
  Municipal notes.......................     500,000          --           --          500,000
                                          ----------      ------        -----       ----------
                                          $4,609,364      $3,098        $  --       $4,612,462
                                          ==========      ======        =====       ==========
July 4, 1998 -- (unaudited)
  U.S. Government debt securities
     (weighted average maturity of 20
     months)............................  $1,003,374      $1,166        $  --       $1,004,540
  Corporate debt securities (weighted
     average maturity of 16 months).....   3,624,427          --         (823)       3,623,604
  Municipal notes (weighted average
     maturity of 18 months).............   2,199,669       3,050           --        2,202,719
                                          ----------      ------        -----       ----------
                                          $6,827,470      $4,216        $(823)      $6,830,863
                                          ==========      ======        =====       ==========
</TABLE>
    
 
     Gross realized gains and losses on the sales of investments have not been
material to the Company's financial statements.
 
                                      F-11
<PAGE>   69
                          ASPECT MEDICAL SYSTEMS, INC.
 
                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)
                (INCLUDING DATA APPLICABLE TO UNAUDITED PERIODS)
 
(4)  INVESTMENT IN SALES-TYPE LEASES
 
     The Company leases equipment to customers under sales-type leases. The
components of the Company's net investment in sales-type leases are as follows:
 
   
<TABLE>
<CAPTION>
                                                           DECEMBER 31,      JULY 4,
                                                               1997           1998
                                                           ------------    -----------
                                                                           (UNAUDITED)
<S>                                                        <C>             <C>
Total minimum lease payments receivable..................    $505,474      $2,449,252
  Less -- unearned interest..............................     160,008       1,015,483
                                                             --------      ----------
Net investment in sales-type leases......................     345,466       1,433,769
  Less -- current portion................................     136,392         531,556
                                                             --------      ----------
                                                             $209,074      $  902,213
                                                             ========      ==========
</TABLE>
    
 
     Future minimum lease payments due under noncancelable leases as of December
31, 1997 are as follows:
 
<TABLE>
<CAPTION>
YEAR ENDING
- -----------
<S>                                                             <C>
1998........................................................    $222,565
1999........................................................     165,443
2000........................................................      79,455
2001........................................................      21,554
2002........................................................      16,457
                                                                --------
                                                                $505,474
                                                                ========
</TABLE>
 
(5)  INVENTORY
 
     Inventory consists of the following:
 
   
<TABLE>
<CAPTION>
                                                    DECEMBER 31,
                                               ----------------------      JULY 4,
                                                  1996         1997         1998
                                               ----------    --------    -----------
                                                                         (UNAUDITED)
<S>                                            <C>           <C>         <C>
Raw materials................................  $  363,205    $322,636     $626,049
Work-in-progress.............................      59,928          --           --
Finished goods...............................     676,704      64,843      325,080
                                               ----------    --------     --------
                                               $1,099,837    $387,479     $951,129
                                               ==========    ========     ========
</TABLE>
    
 
                                      F-12
<PAGE>   70
                          ASPECT MEDICAL SYSTEMS, INC.
 
                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)
                (INCLUDING DATA APPLICABLE TO UNAUDITED PERIODS)
 
(6)  PROPERTY AND EQUIPMENT
 
     Property and equipment consist of the following:
 
   
<TABLE>
<CAPTION>
                                                                DECEMBER 31,
                                     USEFUL LIFE           ----------------------     JULY 4,
                                       IN YEARS              1996         1997         1998
                              --------------------------   ---------   ----------   -----------
                                                                                    (UNAUDITED)
<S>                           <C>                          <C>         <C>          <C>
Computer equipment..........              3                $ 454,414   $  707,071   $1,211,970
Construction in progress....              --                      --      490,194      369,870
Machinery and equipment.....            3 - 5                     --      152,735      383,549
Furniture and fixtures......              3                  123,039      133,114      375,140
                              Shorter of the life of the
                                lease or the estimated
Leasehold improvements......    remaining useful life             --        1,485      270,192
                                                           ---------   ----------   ----------
                                                             577,453    1,484,599    2,610,721
Accumulated depreciation and
  amortization..............                                (368,469)    (561,040)    (713,886)
                                                           ---------   ----------   ----------
                                                           $ 208,984   $  923,559   $1,896,835
                                                           =========   ==========   ==========
</TABLE>
    
 
   
     At December 31, 1996, 1997 and April 4, 1998, property and equipment held
under capital leases totaled approximately $521,651. Accumulated amortization of
these assets totaled approximately $365,515 and $458,988 at December 31, 1996
and 1997, respectively, and $484,769 at July 4, 1998.
    
 
     During 1995 and 1996, the Company entered into sale-leaseback transactions.
The Company received proceeds of approximately $239,000 and $330,000 during 1995
and 1996, respectively, from the sale of these assets. No gain was recorded
during 1995 as the net book value of the assets sold approximated the proceeds
received. A gain of approximately $99,000 relating to the sale-leaseback
transaction was deferred in 1996 and is being amortized over the term of the
respective lease.
 
(7)  INCOME TAXES
 
     Deferred income tax assets consist of the following:
 
<TABLE>
<CAPTION>
                                                               DECEMBER 31,
                                                       ----------------------------
                                                           1996            1997
                                                       ------------    ------------
<S>                                                    <C>             <C>
Net operating loss carryforwards.....................  $  9,009,000    $ 12,254,000
Tax credit carryforwards.............................     1,038,000       1,119,000
Other................................................       315,000         782,000
                                                       ------------    ------------
     Gross deferred tax assets.......................    10,362,000      14,155,000
     Valuation allowance.............................   (10,362,000)    (14,155,000)
                                                       ------------    ------------
     Net deferred tax asset..........................  $         --    $         --
                                                       ============    ============
</TABLE>
 
     The Company has provided a full valuation allowance against its gross
deferred tax assets at December 31, 1996 and 1997 because the future
realizability of such asset is uncertain. Should the Company achieve
profitability in the future, various components of the gross deferred tax assets
would be available to offset future income tax liabilities and expenses.
 
     The Company has net operating loss and research and development tax credit
carryforwards for federal income tax purposes of approximately $30,430,000 and
$1,119,000, respectively, at December 31, 1997 that will expire commencing in
the year 2002 through the year 2012 if not utilized.
 
                                      F-13
<PAGE>   71
                          ASPECT MEDICAL SYSTEMS, INC.
 
                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)
                (INCLUDING DATA APPLICABLE TO UNAUDITED PERIODS)
 
     The net operating loss and research and development tax credit
carryforwards are subject to review by the Internal Revenue Service. Ownership
changes, as defined in the Internal Revenue Code, may limit the amount of these
tax attributes that can be utilized annually to offset future taxable income or
tax liabilities. The amount of the annual limitation is determined based on the
Company's value immediately prior to the ownership change. Subsequent ownership
changes may further affect the limitation in future years.
 
(8)  STOCKHOLDERS' EQUITY
 
  Authorized Capital Stock
 
     As of December 31, 1997, the Company's authorized capital stock consisted
of 10,600,000 shares of common stock, $.01 par value, and 7,707,326 shares of
preferred stock, $.01 par value. Of the 7,707,326 shares of preferred stock,
406,898 shares are designated Series A-1 convertible preferred stock, 3,800,428
shares are designated Series B-1 convertible preferred stock and 3,500,000
shares are designated Series C convertible preferred stock.
 
   
     In February 1998, the Company restated its Certificate of Incorporation. As
a result, the authorized capital stock increased to 14,500,000 shares of common
stock, $.01 par value, and 18,843,224 shares of preferred stock, $.01 par value.
Of the 18,843,224 shares of preferred stock, 406,898 shares are designated
Series A-1 convertible preferred stock, 3,800,428 shares are designated Series
B-1 convertible preferred stock, 3,500,000 shares are designated Series C
convertible preferred stock, 1,714,286 shares are designated Series D
convertible preferred stock, 406,898 shares are designated Series A-2
convertible preferred stock, 3,800,428 shares are designated Series B-2
convertible preferred stock, 3,500,000 shares are designated Series C-2
convertible preferred stock and 1,714,286 shares are designated Series D-2
convertible preferred stock.
    
 
     Upon the closing of the Company's initial public offering, the authorized
capital stock of the Company will consist of 40,000,000 shares of common stock
and 5,000,000 shares of preferred stock, the terms of which will not be
designated.
 
  Convertible Preferred Stock
 
     Convertible preferred stock outstanding consists of the following:
 
   
<TABLE>
<CAPTION>
                                                          DECEMBER 31,
                                                    -------------------------     JULY 4,
                                                       1996          1997          1998
                                                    -----------   -----------   -----------
                                                                                (UNAUDITED)
<S>                                                 <C>           <C>           <C>
Series A-1 convertible preferred stock; 406,898
  shares issued and outstanding, at issuance
  price, net of issuance costs....................  $18,384,462   $18,384,462   $18,384,462
Series B-1 convertible preferred stock; 3,800,428
  shares issued and outstanding, at issuance
  price, net of issuance costs....................    7,506,808     7,506,808     7,506,808
Series C convertible preferred stock; 3,439,949
  shares issued and outstanding, at issuance
  price, net of issuance costs....................           --    12,834,800    12,834,800
Series D convertible preferred stock; 1,666,234
  shares issued and outstanding, at issuance
  price, net of issuance costs....................           --            --    11,573,816
                                                    -----------   -----------   -----------
                                                    $25,891,270   $38,726,070   $50,299,886
                                                    ===========   ===========   ===========
</TABLE>
    
 
                                      F-14
<PAGE>   72
                          ASPECT MEDICAL SYSTEMS, INC.
 
                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)
                (INCLUDING DATA APPLICABLE TO UNAUDITED PERIODS)
 
     In November 1995 and June 1996, the Company sold 2,075,042 and 1,725,386
shares, respectively, of Series B-1 convertible preferred stock in a private
placement, for total net proceeds of $7,506,808 including the conversion of
$500,000 of notes payable to certain stockholders that were issued in 1995. As a
result of anti-dilution provisions associated with this transaction and an
associated recapitalization of the Company, certain preferred stockholders
received an additional 357,761 shares of Series A-1 convertible preferred stock.
 
     In 1997, the Company issued 3,439,949 shares of Series C convertible
preferred stock for net proceeds of $12,834,800.
 
   
     In February 1998, the Company issued 1,666,234 shares of Series D
convertible preferred stock for net proceeds of $11,573,816.
    
 
     The rights and preferences of the Company's convertible preferred stock are
as follows:
 
  Voting Rights
 
     Except as set forth in the Certificate of Incorporation, the holders of the
preferred stock vote together with the holders of common stock as a single class
on all matters. Each preferred stockholder is entitled to the number of votes
equal to the number of whole shares of common stock into which such
stockholder's shares are convertible.
 
  Conversion
 
     Each preferred share is convertible into common stock at the option of the
stockholder or automatically upon the closing of a public offering of the
Company's common stock at a price per common share equal to or exceeding $12.00,
and that results in gross proceeds to the Company of at least $20,000,000. The
number of shares of common stock into which holders of the preferred stock shall
be entitled upon conversion is one-for-one, subject to adjustment for certain
dilutive events.
 
  Liquidation, Dissolution or Winding Up of the Company
 
     In the event of any liquidation, dissolution or winding up of the Company,
the Series A-1 convertible preferred stockholders will receive $22.76 per share,
the Series B-1 convertible preferred stockholders will receive $2.00 per share,
the Series C convertible preferred stockholders will receive $3.75 per share and
the Series D convertible preferred stockholders will receive $7.00 per share. In
the case where the remaining assets of the Company available for distribution
are insufficient to pay the preferred stockholders the full amount they are
entitled to, the preferred stockholders shall share ratably in any distribution
of the assets. Any amounts available after these distributions are to be
distributed to the holders of common stock.
 
  Dividends
 
     The holders of the preferred stock are entitled to dividends when and if
declared by the Board of Directors.
 
  Common Stock
 
   
     At July 4, 1998, the Company has reserved approximately 9,313,509 shares of
common stock for issuance upon conversion of the preferred stock and 1,900,459
shares of common stock for issuance under the Company's stock option plans. On
July 9, 1998, the Company reserved an additional
    
 
                                      F-15
<PAGE>   73
                          ASPECT MEDICAL SYSTEMS, INC.
 
                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)
                (INCLUDING DATA APPLICABLE TO UNAUDITED PERIODS)
 
   
2,150,000 shares of common stock for issuance under the Company's stock option
plans and employee stock purchase plan (see Note 9).
    
 
(9)  STOCK OPTION PLANS
 
  1991 Restated Stock Option Plan
 
   
     The Company's 1991 Restated Stock Option Plan (the "1991 Plan") provides
for the granting, at the discretion of the Board of Directors, of options for
the purchase of up to 3,460,000 shares of common stock to employees, directors
and advisors. Option prices are determined by the Board of Directors. On July 9,
1998, the Board of Directors decreased the number of shares authorized for
issuance upon exercise of stock options under the 1991 Plan to 3,360,000.
    
 
     A summary of plan activity is as follows:
 
   
<TABLE>
<CAPTION>
                                                                                   WEIGHTED
                                                 NUMBER OF     OPTION PRICE     AVERAGE OPTION
                                                   SHARES        PER SHARE      PRICE PER SHARE
                                                 ----------   ---------------   ---------------
<S>                                              <C>          <C>               <C>
Outstanding, December 31, 1994.................      14,151   $16.67 - $45.83       $31.02
  Granted......................................   1,106,532      .20 -  45.83          .22
  Exercised....................................        (166)   16.67 -  45.83        16.91
  Canceled.....................................     (14,507)   16.67 -  45.83        34.78
                                                 ----------   ---------------       ------
Outstanding, December 31, 1995.................   1,106,010      .20 -  45.83          .32
  Granted......................................     451,002               .20          .20
  Exercised....................................          --                --
  Canceled.....................................        (939)              .20          .20
                                                 ----------   ---------------       ------
Outstanding, December 31, 1996.................   1,556,073      .20 -  45.83          .28
  Granted......................................   1,046,532      .20 -    .80          .66
  Exercised....................................  (1,460,450)     .20 -   .375          .22
  Canceled.....................................     (71,529)     .20 -   .375          .20
                                                 ----------   ---------------       ------
Outstanding, December 31, 1997.................   1,070,626      .20 -  45.83          .74
  Granted (unaudited)..........................     416,796      .80 -  11.05         5.00
  Exercised (unaudited)........................    (204,938)     .20 -    .80          .70
  Canceled (unaudited).........................     (10,115)     .20 -  45.83          .57
                                                 ----------   ---------------       ------
Outstanding, July 4, 1998 (unaudited)..........   1,272,369     $.20 - $45.83       $ 2.04
                                                 ==========   ===============       ======
Exercisable, July 4, 1998 (unaudited)..........     260,353     $.20 - $45.83       $  .52
                                                 ==========   ===============       ======
</TABLE>
    
 
   
     Subsequent to July 4, 1998, the Company granted stock options to purchase
430,098 shares of common stock at an exercise price of $11.05 per share, and
stock options to purchase 500 shares of common stock with an exercise price of
$.80 per share were exercised.
    
 
   
     During 1997 and 1998, employees and directors exercised stock options to
purchase an aggregate of 1,407,970 shares and 87,500 shares, respectively, of
restricted common stock. The shares are subject to repurchase by the Company, at
prices ranging from $.20 to $.80 per share. The payment for the restricted
common stock was in the form of cash of $45,735 and full recourse notes of
$336,579 payable to the Company. As of July 4, 1998, an aggregate of 531,850
shares are subject to repurchase.
    
 
                                      F-16
<PAGE>   74
                          ASPECT MEDICAL SYSTEMS, INC.
 
                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)
                (INCLUDING DATA APPLICABLE TO UNAUDITED PERIODS)
 
   
     Stock options and restricted common stock granted under the 1991 Plan
generally vest over two to four years and provide for acceleration of vesting
upon a change of control of the Company.
    
 
   A summary of outstanding and exercisable options as of July 4, 1998 is as
                                    follows:
 
   
<TABLE>
<CAPTION>
                             WEIGHTED
                              AVERAGE
                             REMAINING
  EXERCISE      NUMBER      CONTRACTUAL     NUMBER
   PRICE      OUTSTANDING      LIFE       EXERCISABLE
- ------------  -----------   -----------   -----------
<S>           <C>           <C>           <C>
   $ 0.20        203,066       7.84         140,461
     0.375       113,886       8.87          31,877
     0.80        603,682       9.28          77,815
     2.80        163,365       9.78           9,980
     7.00        125,000       9.95               0
    11.05         63,150       9.95               0
    16.67            207       2.12             207
    45.83             13       2.50              13
- ------------   ---------       ----         -------
$0.20-$45.83   1,272,369       9.19         260,353
</TABLE>
    
 
   
     In connection with certain stock option grants, the Company recorded
deferred compensation of approximately $834,000, which represents the aggregate
difference between the estimated fair market value of the common stock and the
exercise price of the options. This deferred compensation will be recognized as
compensation expense over the vesting term of the options.
    
 
     In October 1995, the Financial Accounting Standards Board (FASB) issued
SFAS No. 123, Accounting for Stock-Based Compensation. SFAS No. 123 requires the
measurement of the fair value of stock options or warrants to be included in the
statement of income or disclosed in the notes to financial statements. The
Company has determined that it will continue to account for stock-based
compensation for employees under Accounting Principles Board Opinion No. 25 and
elect the disclosure-only alternative under SFAS No. 123. The Company has
computed the value of options granted in 1995, 1996 and 1997 using the
Black-Scholes option-pricing model prescribed by SFAS No. 123. The following
table shows the weighted average assumptions used in the applicable periods and
the weighted average fair market value of the options granted in each period.
 
   
<TABLE>
<CAPTION>
                                                                         SIX MONTHS ENDED
                                      YEAR ENDED DECEMBER 31,         -----------------------
                                -----------------------------------    JUNE 28,     JULY 4,
                                  1995         1996         1997         1997         1998
                                ---------   ----------   ----------   ----------   ----------
<S>                             <C>         <C>          <C>          <C>          <C>
Risk-free interest rate.......  5.9%-6.2%    6.4%-6.8%   6.5%-6.75%    6.4%-6.8%   5.1%-6.75%
Expected dividend yield.......         --           --           --           --           --
Expected life.................    7 years      7 years      7 years      7 years      7 years
Expected volatility...........         60%          60%          60%          60%          60%
Weighted average fair market
  value of options granted....  $     .16   $      .15   $      .48   $      .27   $     4.46
</TABLE>
    
 
                                      F-17
<PAGE>   75
                          ASPECT MEDICAL SYSTEMS, INC.
 
                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)
                (INCLUDING DATA APPLICABLE TO UNAUDITED PERIODS)
 
     Had compensation cost for these options been determined consistent with
SFAS No. 123, the Company's net loss and pro forma net loss per common share
would have been increased to the following pro forma amounts:
 
   
<TABLE>
<CAPTION>
                                                                              SIX MONTHS ENDED
                                       YEAR ENDED DECEMBER 31,            -------------------------
                               ----------------------------------------    JUNE 28,       JULY 4,
                                  1995          1996           1997          1997          1998
                               -----------   -----------   ------------   -----------   -----------
                                                                          (UNAUDITED)   (UNAUDITED)
<S>                            <C>           <C>           <C>            <C>           <C>
Net loss
  As reported................  $(5,545,909)  $(5,396,438)  $ (9,885,855)  $(4,447,407)  $(6,517,068)
                               ===========   ===========   ============   ===========   ===========
  Pro forma..................  $(5,590,110)  $(5,457,382)  $(10,073,236)  $(4,541,097)  $(6,676,033)
                               ===========   ===========   ============   ===========   ===========
Basic and diluted net loss
  per common share
  As reported................     $(281.65)      $(57.76)       $(16.23)      $(10.88)       $(6.34)
                               ===========   ===========   ============   ===========   ===========
  Pro forma..................     $(283.89)      $(58.42)       $(16.54)      $(11.10)       $(6.50)
                               ===========   ===========   ============   ===========   ===========
Pro forma basic and diluted
  net loss per common share
  As reported................                                    $(1.28)                     $(0.65)
                                                           ============                 ===========
  Pro forma..................                                    $(1.31)                     $(0.67)
                                                           ============                 ===========
</TABLE>
    
 
     The Black-Scholes option-pricing model was developed for use in estimating
the fair value of traded options which have no vesting restrictions and are
fully transferable. In addition, option-pricing models require the input of
highly subjective assumptions, including expected stock price volatility.
Because the Company's employee stock options have characteristics significantly
different from those of traded options, and because changes in the subjective
input assumptions can materially affect the fair value estimate, in management's
opinion, the existing models do not necessarily provide a reliable single
measure of the fair value of its employee stock options. Also, because options
vest over several years and the Company expects to grant options in future
years, the above pro forma results of applying the provisions of SFAS No. 123
are not necessarily representative of the pro forma results in future years.
 
   
  1998 Stock Incentive Plan
    
 
   
     The Company's 1998 Stock Incentive Plan (the "Incentive Plan") was adopted
by the Board of Directors on July 9, 1998, subject to stockholder approval, and
is intended to replace the 1991 Plan. The Board of Directors has authorized the
Compensation Committee to administer the Incentive Plan, including the granting
of options to executive officers. The Incentive Plan provides for the granting,
at the discretion of the Compensation Committee, of options for the purchase of
up to 2,100,000 shares of common stock (subject to adjustment in the event of
stock splits and other similar events) to employees, directors and advisors.
Option prices are determined by the Compensation Committee, but cannot be less
than 100% of fair market value for incentive stock options (or less than 110% of
the fair market value in the case of incentive stock options granted to
optionees holding more than 10% of the voting power of the Company).
    
 
                                      F-18
<PAGE>   76
                          ASPECT MEDICAL SYSTEMS, INC.
 
                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)
                (INCLUDING DATA APPLICABLE TO UNAUDITED PERIODS)
 
   
  1998 Employee Stock Purchase Plan
    
 
   
     On July 9, 1998, the Company's 1998 Employee Stock Purchase Plan ("Purchase
Plan") was adopted by the Board of Directors, subject to stockholder approval.
The Purchase Plan allows eligible employees the right to purchase common stock
at the lower of 85% of the closing price per share of common stock on the first
or last day of the offering period. Each offering period is six months. An
aggregate of 150,000 shares of common stock have been reserved for issuance
pursuant to the Purchase Plan.
    
 
  1998 Director Stock Option Plan
 
   
     In February 1998, the Company adopted the 1998 Director Stock Option Plan
("Director Plan"). Under the terms of this plan, directors of the Company who
are not employees of the Company are eligible to receive nonstatutory options to
purchase shares of common stock. A total of 100,000 shares of common stock may
be issued upon exercise of options under this plan. The initial options granted
under the Director Plan are exercisable as to 50% of the option as of the date
of grant and as to one-sixth of the shares on the first, second and third
anniversaries of the date of grant, provided that the optionee continues to
serve as a director and provide for the acceleration of vesting upon a change of
control of the Company. Additional options granted will be exercisable in three
equal annual installments on each of the first, second and third anniversaries
of the date of grant, provided that the optionee continues to serve as a
director. Options granted under the Director Plan terminate on the earlier of
(i) ten years from the date of grant, or (ii) sixty days after the optionee
ceases to serve as a director. In April 1998, options to purchase 40,000 shares
were granted under this plan at an exercise price of $2.80, of which 20,000
shares are exercisable at July 4, 1998. In connection with these grants, the
Company recorded deferred compensation of approximately $56,000 which
represented the difference between the estimated fair market value of the common
stock and the exercise price of the options. This deferred compensation will be
recognized as compensation expense over the vesting term of the options.
    
 
(10)  NET LOSS PER SHARE
 
   
     The Company follows Statement of Financial Accounting Standards (SFAS) No.
128, Earnings per Share. Basic net loss per share represents net loss available
to common stockholders divided by the weighted average number of common shares
outstanding. The Company has excluded all shares of restricted common stock that
are subject to repurchase by the Company from the weighted average number of
common shares outstanding. Diluted net loss per share is the same as basic net
loss per share for the Company, because all stock options and convertible
preferred stock have been excluded from the calculation. Inclusion of stock
issuable pursuant to the exercise of stock options and the conversion of
convertible preferred stock would be antidilutive. The Company evaluated the
requirements of the Securities and Exchange Commission Staff Accounting Bulletin
No. 98 ("SAB 98"), and concluded that there are no nominal issuances of common
stock or common stock equivalents which would be required to be shown as
outstanding for all periods as outlined in SAB 98. Pro forma net loss per share
includes the weighted average common shares outstanding and reflects the
automatic conversion of all convertible preferred stock into common stock upon
completion of the Company's initial public offering based on the original
issuance date using the "if-converted" method.
    
 
                                      F-19
<PAGE>   77
                          ASPECT MEDICAL SYSTEMS, INC.
 
                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)
                (INCLUDING DATA APPLICABLE TO UNAUDITED PERIODS)
 
(11)  DISTRIBUTION AND LICENSING AGREEMENTS
 
   
     The Company has entered into various distribution, licensing and royalty
agreements relating to its monitor products with distributors covering the
international market. These agreements have terms ranging from three to ten
years. In connection with these agreements, approximately $823,000 and $643,000
in revenue was deferred as of December 31, 1996 and 1997, respectively, and
approximately $1,520,500 was deferred as of July 4, 1998. The deferred revenue
relates to prepayments for monitoring systems under minimum purchase obligations
and also includes prepaid license and royalty fees. The deferred revenue will be
recognized upon product shipment and as license and royalty fees are earned.
License and royalty fees are related to future technological developments and
will be recognized upon shipment of units incorporating this technology.
    
 
(12)  401(K) SAVINGS PLAN
 
     The Company has a 401(k) savings plan in which substantially all employees
can participate. Employer contributions are at the discretion of the Board of
Directors and vest ratably over five years. The Company made no contributions to
the plan during the years ended December 31, 1995, 1996 and 1997.
 
(13)  COMMITMENTS AND CONTINGENCIES
 
  Leases
 
     The Company leases office space under an operating lease and certain
equipment under capital leases. Rent expense was approximately $328,000,
$335,000 and $346,000 in 1995, 1996 and 1997, respectively. Future gross minimum
lease commitments as of December 31, 1997 are as follows:
 
<TABLE>
<CAPTION>
                                                       OPERATING LEASES    CAPITAL LEASES
                                                       ----------------    --------------
<S>                                                    <C>                 <C>
1998.................................................     $  406,298          $169,016
1999.................................................        397,528           135,960
2000.................................................        331,273                --
                                                          ----------          --------
Total minimum lease payments.........................     $1,135,099           304,976
                                                          ==========
Less -- Amount representing interest.................                           32,390
                                                                              --------
Present value of obligations under capital leases....                          272,586
Less -- Current portion..............................                          154,906
                                                                              --------
                                                                              $117,680
                                                                              ========
</TABLE>
 
  Subleases
 
     During 1995, 1996 and 1997, the Company had a sublease agreement whereby a
portion of existing office space was leased to a third party under an operating
lease. Rental income for 1995, 1996 and 1997 approximated $15,000, $129,000 and
$113,000, respectively. This agreement expired in 1997.
 
(14)  OTHER RELATED PARTY TRANSACTIONS
 
     In addition to the transactions discussed in Note 9, during 1997 the
Company loaned a total of $107,000 to certain employees of the Company. The
loans are evidenced by promissory notes
 
                                      F-20
<PAGE>   78
                          ASPECT MEDICAL SYSTEMS, INC.
 
                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)
                (INCLUDING DATA APPLICABLE TO UNAUDITED PERIODS)
 
   
bearing interest with rates ranging from 6.42% to 8% per annum. The outstanding
balance on these notes at December 31, 1997 and July 4, 1998 was approximately
$105,000 and $92,000, respectively.
    
 
(15)  ACCRUED LIABILITIES
 
     Accrued liabilities consist of the following:
 
   
<TABLE>
<CAPTION>
                                                    DECEMBER 31,
                                               ----------------------      JULY 4,
                                                 1996         1997          1998
                                               --------    ----------    -----------
                                                                         (UNAUDITED)
<S>                                            <C>         <C>           <C>
Payroll and payroll-related..................  $ 80,163    $  375,121    $  642,460
Other........................................   644,168     1,125,470     2,291,294
                                               --------    ----------    ----------
                                               $724,331    $1,500,591    $2,933,754
                                               ========    ==========    ==========
</TABLE>
    
 
(16)  FINANCIAL INFORMATION BY GEOGRAPHIC AREA
 
     Revenues by geographic destination and as a percentage of total revenues
are as follows:
 
   
<TABLE>
<CAPTION>
                              YEAR ENDED DECEMBER 31,                   SIX MONTHS ENDED
                       --------------------------------------    -------------------------------
                          1995          1996          1997       JUNE 28, 1997     JULY 4, 1998
                       ----------    ----------    ----------    --------------    -------------
                                                                  (UNAUDITED)       (UNAUDITED)
<S>                    <C>           <C>           <C>           <C>               <C>
GEOGRAPHIC AREA BY
DESTINATION
  Domestic...........  $  563,857    $  699,362    $1,881,409      $  640,104       $3,794,447
  International......     503,350       689,426     1,186,164         435,703          625,718
                       ----------    ----------    ----------      ----------       ----------
                       $1,067,207    $1,388,788    $3,067,573      $1,075,807       $4,420,165
                       ==========    ==========    ==========      ==========       ==========
</TABLE>
    
 
   
<TABLE>
<CAPTION>
                                       YEAR ENDED DECEMBER 31,              SIX MONTHS ENDED
                                      -------------------------     --------------------------------
                                      1995      1996      1997      JUNE 28, 1997      JULY 4, 1998
                                      -----     -----     -----     --------------     -------------
                                                                     (UNAUDITED)        (UNAUDITED)
<S>                                   <C>       <C>       <C>       <C>                <C>
GEOGRAPHIC AREA BY DESTINATION
  Domestic..........................    53%       51%       61%           60%                86%
  International.....................    47        49        39            40                 14
                                       ---       ---       ---           ---                ---
                                       100%      100%      100%          100%               100%
                                       ===       ===       ===           ===                ===
</TABLE>
    
 
(17)  VALUATION AND QUALIFYING ACCOUNTS
 
     The following table sets forth activity in the Company's allowance for
doubtful accounts:
 
   
<TABLE>
<CAPTION>
                                            BALANCE AT                                 BALANCE AT
                                           BEGINNING OF    CHARGES TO                    END OF
                                              PERIOD        EXPENSES     DEDUCTIONS      PERIOD
                                           ------------    ----------    ----------    ----------
<S>                                        <C>             <C>           <C>           <C>
Year Ended --
  December 31, 1995......................    $ 8,000        $    --        $1,000       $ 7,000
  December 31, 1996......................      7,000         43,000            --        50,000
  December 31, 1997......................     50,000         14,333         1,933        62,400
Six months ended July 4, 1998............     62,400         40,000            90       102,310
</TABLE>
    
 
(18)  LOAN AGREEMENT
 
     In June 1998, the Company entered into a loan agreement with a commercial
bank. Under the terms of this loan agreement, the Company may borrow up to $5.0
million for working capital and equipment. The amount available to the Company
under the working capital portion of the loan
 
                                      F-21
<PAGE>   79
                          ASPECT MEDICAL SYSTEMS, INC.
 
                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)
                (INCLUDING DATA APPLICABLE TO UNAUDITED PERIODS)
 
agreement is based upon a percentage of the Company's outstanding accounts
receivable. The outstanding principal under the working capital portion of the
loan agreement is due and payable in December 1999. Interest on the working
capital portion of the loan agreement is at the prime rate plus .5% until
September 30, 1998 whereby it becomes the prime rate plus .25%.
 
     The principal amount outstanding under the equipment portion of the loan
agreement is due in 36 equal monthly installments commencing in January 1999.
Interest on the equipment loan portion of the loan agreement is at the prime
rate plus 1.0% up to and including the closing date of the Company's initial
public offering. After the closing of the Company's initial public offering, the
interest rate becomes the prime rate.
 
   
     The loan agreement contains certain restrictive covenants that require the
Company to maintain minimum liquidity or debt service coverage ratios. The
agreement also restricts the Company from declaring and paying cash dividends.
    
 
   
     At July 4, 1998, approximately $776,000 was outstanding under the equipment
portion of the loan agreement. There were no outstanding balances under the
working capital portion of the loan agreement at July 4, 1998.
    
 
                                      F-22
<PAGE>   80
 
   
                       [INSIDE BACK COVER OF PROSPECTUS]
    
 
   
     Each year, approximately 29 million patients in the United States and 42
million patients in Europe and Japan receive anesthesia for surgical procedures.
Aspect's clinically validated BIS index assists the anesthesia provider in
assessing levels of consciousness and administering appropriate amounts of
anesthetics.
    
 
   
     [Photograph depicting an anesthesia provider sitting next to a patient
being monitored with the Company's BIS monitor product.]
    
 
   
     Benefits of BIS monitoring demonstrated by the Company in a 302-patient
prospective, randomized, controlled clinical utility trial include:
    
 
   
     - more controlled and cost-effective dosing of anesthetic drugs
    
 
   
     - faster and more predictable recovery from anesthesia
    
 
   
     - improved quality of recovery
    
 
   
     [Photograph depicting a patient sitting in a chair holding a beverage.]
    
 
   
     Other studies have shown that, when appropriate levels of anesthesia are
administered, patients are more likely to meet criteria for bypassing the PACU
following ambulatory surgery and proceeding immediately to the less costly
step-down recovery area.
    
 
   
                                          [Company Logo]
    
<PAGE>   81
 
- ------------------------------------------------------
- ------------------------------------------------------
 
  NO DEALER, SALESPERSON OR ANY OTHER PERSON HAS BEEN AUTHORIZED TO GIVE ANY
INFORMATION OR TO MAKE ANY REPRESENTATION IN CONNECTION WITH THIS OFFERING OTHER
THAN THOSE CONTAINED IN THIS PROSPECTUS, AND, IF GIVEN OR MADE, SUCH INFORMATION
OR REPRESENTATION MUST NOT BE RELIED UPON AS HAVING BEEN AUTHORIZED BY THE
COMPANY OR ANY UNDERWRITER. NEITHER THE DELIVERY OF THIS PROSPECTUS NOR ANY SALE
MADE HEREUNDER SHALL, UNDER ANY CIRCUMSTANCES, CREATE ANY IMPLICATION THAT THERE
HAS BEEN NO CHANGE IN THE AFFAIRS OF THE COMPANY SINCE THE DATE HEREOF OR THAT
THE INFORMATION CONTAINED HEREIN IS CORRECT AS OF ANY TIME SUBSEQUENT TO THE
DATE HEREOF. THIS PROSPECTUS DOES NOT CONSTITUTE AN OFFER TO SELL, OR
SOLICITATION OF AN OFFER TO BUY, ANY SECURITIES OTHER THAN THE REGISTERED
SECURITIES TO WHICH IT RELATES, OR AN OFFER TO SELL TO, OR SOLICITATION OF, ANY
PERSON IN ANY CIRCUMSTANCES IN WHICH SUCH OFFER OR SOLICITATION IS UNLAWFUL.
 
                             ---------------------
 
                               TABLE OF CONTENTS
 
   
<TABLE>
<CAPTION>
                                        PAGE
                                        ----
<S>                                     <C>
Prospectus Summary....................    3
Risk Factors..........................    5
Use of Proceeds.......................   13
Dividend Policy.......................   13
Capitalization........................   14
Dilution..............................   15
Selected Financial Information........   16
Management's Discussion and Analysis
  of Financial Condition and Results
  of Operations.......................   17
Business..............................   22
Management............................   37
Certain Transactions..................   45
Principal Stockholders................   47
Description of Capital Stock..........   50
Shares Eligible for Future Sale.......   52
Underwriting..........................   54
Legal Matters.........................   55
Experts...............................   55
Additional Information................   55
Index to Financial Statements.........  F-1
</TABLE>
    
 
                            ------------------------

  UNTIL                , 1998 (25 DAYS AFTER THE DATE OF THIS PROSPECTUS), ALL
DEALERS EFFECTING TRANSACTIONS IN THE COMMON STOCK OFFERED HEREBY, WHETHER OR
NOT PARTICIPATING IN THIS DISTRIBUTION, MAY BE REQUIRED TO DELIVER A PROSPECTUS.
THIS IS IN ADDITION TO THE OBLIGATION OF DEALERS TO DELIVER A PROSPECTUS WHEN
ACTING AS UNDERWRITERS AND WITH RESPECT TO THEIR UNSOLD ALLOTMENTS OR
SUBSCRIPTIONS.
 
- ------------------------------------------------------
- ------------------------------------------------------


- ------------------------------------------------------
- ------------------------------------------------------
   
                                3,100,000 Shares
    
 
                         [ASPECT MEDICAL SYSTEMS LOGO]

                                  Common Stock

                              -------------------
                                   PROSPECTUS
                              -------------------
 
                                 BT Alex.Brown
 
                              Merrill Lynch & Co.
 
                               Piper Jaffray Inc.

                                          , 1998

- ------------------------------------------------------
- ------------------------------------------------------

<PAGE>   82
 
                                    PART II
 
                     INFORMATION NOT REQUIRED IN PROSPECTUS
 
ITEM 13.  OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION
 
     The following table sets forth the various expenses, all of which will be
borne by the Registrant, in connection with the sale and distribution of the
securities being registered, other than the underwriting discounts and
commissions. All amounts shown are estimates except for the Securities and
Exchange Commission registration fee and the NASD filing fee.
 
   
<TABLE>
<S>                                                             <C>
SEC registration fee........................................    $ 15,776
NASD filing fee.............................................       5,848
Nasdaq National Market listing fee..........................      88,500
Blue Sky fees and expenses..................................      10,000
Transfer Agent and Registrar fees...........................       5,500
Accounting fees and expenses................................     250,000
Legal fees and expenses.....................................     300,000
Printing and mailing expenses...............................     130,000
Miscellaneous...............................................      44,376
                                                                --------
          Total.............................................    $850,000
                                                                ========
</TABLE>
    
 
ITEM 14.  INDEMNIFICATION OF DIRECTORS AND OFFICERS
 
     Article EIGHTH of the Registrant's Restated Certificate of Incorporation
(the "Restated Certificate of Incorporation") provides that no director of the
Registrant shall be personally liable for any monetary damages for any breach of
fiduciary duty as a director, except to the extent that the Delaware General
Corporation Law prohibits the elimination or limitation of liability of
directors for breach of fiduciary duty.
 
     Article NINTH of the Registrant's Restated Certificate of Incorporation
provides that a director or officer of the Registrant (a) shall be indemnified
by the Registrant against all expenses (including attorneys' fees), judgments,
fines and amounts paid in settlement incurred in connection with any litigation
or other legal proceeding (other than an action by or in the right of the
Registrant) brought against him by virtue of his position as a director or
officer of the Registrant if he acted in good faith and in a manner he
reasonably believed to be in, or not opposed to, the best interests of the
Registrant, and, with respect to any criminal action or proceeding, had no
reasonable cause to believe his conduct was unlawful and (b) shall be
indemnified by the Registrant against all expenses (including attorneys' fees)
and amounts paid in settlement incurred in connection with any action by or in
the right of the Registrant brought against him by virtue of his position as a
director or officer of the Registrant if he acted in good faith and in a manner
he reasonably believed to be in, or not opposed to, the best interests of the
Registrant, except that no indemnification shall be made with respect to any
matter as to which such person shall have been adjudged to be liable to the
Registrant, unless a court determines that, despite such adjudication but in
view of all of the circumstances, he is entitled to indemnification of such
expenses. Notwithstanding the foregoing, to the extent that a director or
officer has been successful, on the merits or otherwise, including, without
limitation, the dismissal of an action without prejudice, he is required to be
indemnified by the Registrant against all expenses (including attorneys' fees)
incurred in connection therewith. Expenses shall be advanced to a director or
officer at his request, provided that he undertakes to repay the amount advanced
if it is ultimately determined that he is not entitled to indemnification for
such expenses.
 
     Indemnification is required to be made unless the Registrant determines
that the applicable standard of conduct required for indemnification has not
been met. In the event of a determination
 
                                      II-1
<PAGE>   83
 
by the Registrant that the director or officer did not meet the applicable
standard of conduct required for indemnification, or if the Registrant fails to
make an indemnification payment within 60 days after such payment is claimed by
such person, such person is permitted to petition the court to make an
independent determination as to whether such person is entitled to
indemnification. As a condition precedent to the right of indemnification, the
director or officer must give the Registrant notice of the action for which
indemnity is sought and the Registrant has the right to participate in such
action or assume the defense thereof.
 
     Article NINTH of the Registrant's Restated Certificate of Incorporation
further provides that the indemnification provided therein is not exclusive, and
provides that in the event that the Delaware General Corporation Law is amended
to expand the indemnification permitted to directors or officers the Registrant
must indemnify those persons to the fullest extent permitted by such law as so
amended.
 
     Section 145 of the Delaware General Corporation Law provides that a
corporation has the power to indemnify a director, officer, employee or agent of
the corporation and certain other persons serving at the request of the
corporation in related capacities against amounts paid and expenses incurred in
connection with an action or proceeding to which he is or is threatened to be
made a party by reason of such position, if such person shall have acted in good
faith and in a manner he reasonably believed to be in or not opposed to the best
interests of the corporation, and, in any criminal proceeding, if such person
had no reasonable cause to believe his conduct was unlawful; provided that, in
the case of actions brought by or in the right of the corporation, no
indemnification shall be made with respect to any matter as to which such person
shall have been adjudged to be liable to the corporation unless and only to the
extent that the adjudicating court determines that such indemnification is
proper under the circumstances.
 
     Under Section 8 of the Underwriting Agreement, the Underwriters are
obligated, under certain circumstances, to indemnify directors and officers of
the Registrant against certain liabilities, including liabilities under the
Securities Act.
 
ITEM 15.  RECENT SALES OF UNREGISTERED SECURITIES
 
   
     Set forth in chronological order is information regarding shares of Common
Stock and Preferred Stock issued and options granted by the Company since July
1, 1995. Further included is the consideration, if any, received by the Company
for such shares and options and information relating to the section of the
Securities Act of 1933, as amended (the "Securities Act"), or rule of the
Securities and Exchange Commission under which exemption from registration was
claimed.
    
 
     Certain of the transactions described below involved directors, officers
and 5% Stockholders of the Company. See "Certain Transactions."
 
   
     The Company's Amended and Restated 1991 Stock Option Plan was adopted by
the Board of Directors and approved by the stockholders of the Company in April
1991, and the Company's 1998 Director Stock Option Plan was adopted by the Board
of Directors and approved by the stockholders of the Company in February 1998.
As of July 4, 1998, options to purchase 1,665,961 of Common Stock had been
exercised for an aggregate consideration of $598,327 and options to purchase
1,312,369 of Common Stock, at a weighted average exercise price of $2.07 per
share, were outstanding under such plans.
    
 
     In November 1995, the Company issued and sold 104 shares of its Common
Stock to LTI Ventures Leasing Corp. at a purchase price of $2.00 per share in
connection with the execution of a Master Lease Agreement.
 
     On November 2, 1995 and June 28, 1996, the Company issued and sold an
aggregate of 3,800,428 shares of its Series B-1 Convertible Preferred Stock to a
group of investors at a purchase price of $2.00 per share.
 
                                      II-2
<PAGE>   84
 
     On February 26, 1997, August 8, 1997 and October 7, 1997, the Company
issued and sold an aggregate of 3,439,949 shares of its Series C Convertible
Preferred Stock to a group of investors at a purchase price of $3.75 per share.
 
     On February 13, 1998, the Company issued and sold an aggregate of 1,666,234
shares of its Series D Convertible Preferred Stock to a group of investors at a
purchase price of $7.00 per share.
 
     The securities issued in the foregoing transactions were either (i) offered
and sold in reliance upon exemptions from Securities Act registration set forth
in Sections 3(b) and 4(2) of the Securities Act, or any regulations promulgated
thereunder, relating to sales by an issuer not involving any public offering, or
(ii) in the case of certain options to purchase shares of Common Stock and
shares of Common Stock issued upon the exercise of such options, such offers and
sales were made in reliance upon an exemption from registration under Rule 701
of the Securities Act. No underwriters were involved in the foregoing sales of
securities.
 
ITEM 16.  EXHIBITS AND FINANCIAL STATEMENT SCHEDULES
 
     (a) Exhibits
 
   
<TABLE>
<CAPTION>
EXHIBIT
  NO.                              DESCRIPTION
- -------                            -----------
<S>        <C>
 1         Form of Underwriting Agreement.
 3.1**     Third Restated Certificate of Incorporation of the Company.
 3.2*      Form of Certificate of Amendment to Third Restated
           Certificate of Incorporation of the Company (to be filed
           immediately prior to the effectiveness of this Registration
           Statement).
 3.3*      Form of Restated Certificate of Incorporation of the Company
           (to be filed upon the closing of the offering to which this
           Registration Statement relates).
 3.4**     By-Laws of the Company, as amended.
 3.5**     Form of Amended and Restated By-Laws of the Company (to be
           effective upon the closing of the offering to which this
           Registration Statement relates).
 4.1*      Specimen certificate for shares of Common Stock, $.01 par
           value, of the Company.
 5*        Opinion of Hale and Dorr LLP.
10.1**     1998 Director Stock Option Plan.
10.2       [Intentionally left blank.]
10.3+**    International Distribution Agreement, dated as of January
           21, 1998, by and between the Company and Nihon Kohden
           Corporation.
10.4+**    International License Agreement, dated as of January 21,
           1998, by and between the Company and Nihon Kohden
           Corporation.
10.5**     Trademark License Agreement, dated May 25, 1994, between
           Aspect Electronics, Inc. and the Company.
10.6+**    License Agreement, dated as of October 31, 1995, between
           Siemens Medical Systems, Inc. and the Company.
10.7**     Property Lease at 2 Vision Drive between the Company and
           Vision Drive, Inc., successor in interest to Natick
           Executive Park Trust No. 2, dated September 8, 1994, as
           amended, together with Subordination, Non-Disturbance and
           Attornment Agreement between the Company and Teachers
           Insurance Association of America, dated June 15, 1995.
10.8**     Lease Extension Agreement, dated as of August 7, 1997,
           between Vision Drive, Inc. and the Company.
</TABLE>
    
 
                                      II-3
<PAGE>   85
 
   
<TABLE>
<CAPTION>
EXHIBIT
  NO.                              DESCRIPTION
- -------                            -----------
<S>        <C>
10.9**     Loan Agreement, dated as of June 22, 1998, between the
           Company and Imperial Bank, together with Revolving Loans
           Promissory Note, dated June 22, 1998, made in favor of
           Imperial Bank by the Company, Equipment Loans Promissory
           Note, dated June 22, 1998, made in favor of Imperial Bank by
           the Company, Security Agreement, dated as of June 22, 1998,
           between the Company and Imperial Bank, Trademark Collateral
           Security and Pledge Agreement, dated as of June 22, 1998,
           between the Company and Imperial Bank, Patent Collateral
           Security and Pledge Agreement, dated as of June 22, 1998,
           between the Company and Imperial Bank and Agreement to
           Provide Insurance, dated June 22, 1998, between the Company
           and Imperial Bank.
10.10**    Promissory Note, dated February 18, 1997, as amended on
           April 14, 1997, made in favor of the Company by Nassib G.
           Chamoun, together with Pledge Agreement, dated as of
           February 18, 1997, as amended on April 14, 1997, between
           Nassib G. Chamoun and the Company.
10.11**    Promissory Note, dated May 1, 1997, made in favor of the
           Company by Nassib G. Chamoun, together with Pledge
           Agreement, dated as of May 1, 1997, between Nassib G.
           Chamoun and the Company.
10.12**    Promissory Note, dated May 1, 1997, made in favor of the
           Company by Nassib G. Chamoun, together with Pledge
           Agreement, dated as of May 1, 1997, between Nassib G.
           Chamoun and the Company.
10.13**    Form of Promissory Note made in favor of the Company by
           certain directors and executive officers, together with Form
           of Pledge Agreement between the Company and certain
           directors and executive officers.
10.14**    Promissory Note, dated September 24, 1997, made in favor of
           the Company by Jeffrey Barrett.
10.15**    Promissory Note, dated April 10, 1998, made in favor of the
           Company by Jeffrey Barrett, together with Pledge Agreement,
           dated as of April 10, 1998, between Jeffrey Barrett and the
           Company.
10.16**    Series D Convertible Preferred Stock Purchase Agreement
           dated February 13, 1998 by and among the Company and the
           several purchasers named on Schedule I thereto.
10.17**    Third Amended and Restated Right of First Refusal and
           Co-Sale Agreement dated February 13, 1998 by and among the
           Company and the several parties named on Schedules I and II
           thereto.
10.18**    Third Amended and Restated Registration Rights Agreement
           dated February 13, 1998 by and among the Company and the
           parties named on the signature pages thereto.
10.19**    Third Amended and Restated Voting Agreement dated February
           13, 1998 by and among the Company and the several parties
           named on Schedule I thereto.
23.1       Consent of Arthur Andersen LLP.
23.2       Consent of PricewaterhouseCoopers LLP.
23.3*      Consent of Hale and Dorr LLP (included in Exhibit 5).
24**       Power of Attorney.
27.1**     Financial Data Schedule for fiscal year ended December 31,
           1997.
27.2       Financial Data Schedule for the six months ended July 4,
           1998.
</TABLE>
    
 
- ---------------
 * To be filed by amendment.
 
   
** Previously filed.
    
 
 + Confidential treatment requested as to certain portions, which portions have
   been omitted and filed separately with the Securities and Exchange
   Commission.
 
     (b) Financial Statement Schedules
 
     All schedules have been omitted because they are not required or because
the required information is given in the Company's Financial Statements or Notes
thereto.
 
                                      II-4
<PAGE>   86
 
ITEM 17.  UNDERTAKINGS
 
     Insofar as indemnification for liabilities arising under the Securities Act
may be permitted to directors, officers and controlling persons of the Company
pursuant to the provisions contained in the Amended and Restated Certificate of
Incorporation of the Company and the laws of the State of Delaware, or
otherwise, the Company has been advised that in the opinion of the Securities
and Exchange Commission such indemnification is against public policy as
expressed in the Securities Act and is, therefore, unenforceable. In the event
that a claim for indemnification against such liabilities (other than the
payment by the Company of expenses incurred or paid by a director, officer or
controlling person of the Company in the successful defense of any action, suit
or proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the Company will, unless in the
opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Securities
Act and will be governed by the final adjudication of such issue.
 
     The undersigned Company hereby undertakes to provide to the Underwriters at
the closing specified in the Underwriting Agreement certificates in such
denominations and registered in such names as required by the Underwriters to
permit prompt delivery to each purchaser.
 
     The undersigned Company hereby undertakes that:
 
          (1) For purposes of determining any liability under the Securities
     Act, the information omitted form the form of prospectus filed as part of
     this Registration Statement in reliance upon Rule 430A and contained in a
     form of prospectus filed by the Company pursuant to Rule 424(b)(1) or (4)
     or 497(h) under the Securities Act shall be deemed to be part of this
     Registration Statement as of the time it was declared effective.
 
          (2) For the purpose of determining any liability under the Securities
     Act, each post-effective amendment that contains a form of prospectus shall
     be deemed to be a new registration statement relating to the securities
     offered therein, and the offering of such securities at that time shall be
     deemed to be the initial bona fide offering thereof.
 
                                      II-5
<PAGE>   87
 
                                   SIGNATURES
 
   
     Pursuant to the requirements of the Securities Act of 1933, the Company has
duly caused this Amendment No. 1 to Registration Statement to be signed on its
behalf by the undersigned, thereunto duly authorized, in Natick, Massachusetts
on this 15th day of July, 1998.
    
 
                                          ASPECT MEDICAL SYSTEMS, INC.
 
   
                                          By:     /s/ J. NEAL ARMSTRONG
    
                                            ------------------------------------
   
                                            J. Neal Armstrong
    
   
                                            Vice President and Chief Financial
                                              Officer
    
 
   
     Pursuant to the requirements of the Securities Act of 1933, this Amendment
No. 1 to Registration Statement has been signed below by the following persons
in the capacities and on the dates indicated.
    
 
   
<TABLE>
<CAPTION>
                   SIGNATURE                                    TITLE                     DATE
                   ---------                                    -----                     ----
<C>                                               <S>                                 <C>
 
             /s/ NASSIB G. CHAMOUN*               Chief Executive Officer and         July 15, 1998
- ------------------------------------------------    President (Principal Executive
               Nassib G. Chamoun                    Officer)
 
           /s/ J. BRECKENRIDGE EAGLE*             Chairman of the Board of Directors  July 15, 1998
- ------------------------------------------------
             J. Breckenridge Eagle
 
             /s/ J. NEAL ARMSTRONG                Vice President and Chief Financial  July 15, 1998
- ------------------------------------------------    Officer (Principal Financial and
               J. Neal Armstrong                    Accounting Officer)
 
              /s/ STEPHEN E. COIT*                Director                            July 15, 1998
- ------------------------------------------------
                Stephen E. Coit
 
            /s/ EDWIN M. KANIA, JR.*              Director                            July 15, 1998
- ------------------------------------------------
               Edwin M. Kania, Jr
                       .
 
              /s/ LESTER J. LLOYD*                Director                            July 15, 1998
- ------------------------------------------------
                Lester J. Lloyd
 
             /s/ TERRANCE MCGUIRE*                Director                            July 15, 1998
- ------------------------------------------------
                Terrance McGuire
 
              /s/ DONALD STANSKI*                 Director                            July 15, 1998
- ------------------------------------------------
                 Donald Stanski
 
           *By: /s/ J. NEAL ARMSTRONG
- ------------------------------------------------
               J. Neal Armstrong
                Attorney-In-Fact
</TABLE>
    
 
                                      II-6
<PAGE>   88
 
                                 EXHIBIT INDEX
 
   
<TABLE>
<CAPTION>
EXHIBIT
  NO.                              DESCRIPTION
- -------                            -----------
<S>        <C>
 1         Form of Underwriting Agreement.
 3.1**     Third Restated Certificate of Incorporation of the Company.
 3.2*      Form of Certificate of Amendment to Third Restated
           Certificate of Incorporation of the Company (to be filed
           immediately prior to the effectiveness of this Registration
           Statement).
 3.3*      Form of Restated Certificate of Incorporation of the Company
           (to be filed upon the closing of the offering to which this
           Registration Statement relates).
 3.4**     By-Laws of the Company, as amended.
 3.5**     Form of Amended and Restated By-Laws of the Company (to be
           effective upon the closing of the offering to which this
           Registration Statement relates).
 4.1*      Specimen certificate for shares of Common Stock, $.01 par
           value, of the Company.
 5*        Opinion of Hale and Dorr LLP.
10.1**     1998 Director Stock Option Plan.
10.2       [Intentionally left blank.]
10.3+**    International Distribution Agreement, dated as of January
           21, 1998, by and between the Company and Nihon Kohden
           Corporation.
10.4+**    International License Agreement, dated as of January 21,
           1998, by and between the Company and Nihon Kohden
           Corporation.
10.5**     Trademark License Agreement, dated May 25, 1994, between
           Aspect Electronics, Inc. and the Company.
10.6+**    License Agreement, dated as of October 31, 1995, between
           Siemens Medical Systems, Inc. and the Company.
10.7**     Property Lease at 2 Vision Drive between the Company and
           Vision Drive, Inc., successor in interest to Natick
           Executive Park Trust No. 2, dated September 8, 1994, as
           amended, together with Subordination, Non-Disturbance and
           Attornment Agreement between the Company and Teachers
           Insurance Association of America, dated June 15, 1995.
10.8**     Lease Extension Agreement, dated as of August 7, 1997,
           between Vision Drive, Inc. and the Company.
10.9**     Loan Agreement, dated as of June 22, 1998, between the
           Company and Imperial Bank, together with Revolving Loans
           Promissory Note, dated June 22, 1998, made in favor of
           Imperial Bank by the Company, Equipment Loans Promissory
           Note, dated June 22, 1998, made in favor of Imperial Bank by
           the Company, Security Agreement, dated as of June 22, 1998,
           between the Company and Imperial Bank, Trademark Collateral
           Security and Pledge Agreement, dated as of June 22, 1998,
           between the Company and Imperial Bank, Patent Collateral
           Security and Pledge Agreement, dated as of June 22, 1998,
           between the Company and Imperial Bank and Agreement to
           Provide Insurance, dated June 22, 1998, between the Company
           and Imperial Bank.
10.10**    Promissory Note, dated February 18, 1997, as amended on
           April 14, 1997, made in favor of the Company by Nassib G.
           Chamoun, together with Pledge Agreement, dated as of
           February 18, 1997, as amended on April 14, 1997, between
           Nassib G. Chamoun and the Company.
10.11**    Promissory Note, dated May 1, 1997, made in favor of the
           Company by Nassib G. Chamoun, together with Pledge
           Agreement, dated as of May 1, 1997, between Nassib G.
           Chamoun and the Company.
10.12**    Promissory Note, dated May 1, 1997, made in favor of the
           Company by Nassib G. Chamoun, together with Pledge
           Agreement, dated as of May 1, 1997, between Nassib G.
           Chamoun and the Company.
10.13**    Form of Promissory Note made in favor of the Company by
           certain directors and executive officers, together with Form
           of Pledge Agreement between the Company and certain
           directors and executive officers.
10.14**    Promissory Note, dated September 24, 1997, made in favor of
           the Company by Jeffrey Barrett.
</TABLE>
    
<PAGE>   89
 
   
<TABLE>
<CAPTION>
EXHIBIT
  NO.                              DESCRIPTION
- -------                            -----------
<S>        <C>
10.15**    Promissory Note, dated April 10, 1998, made in favor of the
           Company by Jeffrey Barrett, together with Pledge Agreement,
           dated as of April 10, 1998, between Jeffrey Barrett and the
           Company.
10.16**    Series D Convertible Preferred Stock Purchase Agreement
           dated February 13, 1998 by and among the Company and the
           several purchasers named on Schedule I thereto.
10.17**    Third Amended and Restated Right of First Refusal and
           Co-Sale Agreement dated February 13, 1998 by and among the
           Company and the several parties named on Schedules I and II
           thereto.
10.18**    Third Amended and Restated Registration Rights Agreement
           dated February 13, 1998 by and among the Company and the
           parties named on the signature pages thereto.
10.19**    Third Amended and Restated Voting Agreement dated February
           13, 1998 by and among the Company and the several parties
           named on Schedule I thereto.
23.1       Consent of Arthur Andersen LLP.
23.2       Consent of PricewaterhouseCoopers LLP.
23.3*      Consent of Hale and Dorr LLP (included in Exhibit 5).
24**       Power of Attorney.
27.1**     Financial Data Schedule for fiscal year ended December 31,
           1997.
27.2       Financial Data Schedule for the six months ended July 4,
           1998.
</TABLE>
    
 
- ---------------
 * To be filed by amendment.
 
** Previously filed.
 
 + Confidential treatment requested as to certain portions, which portions have
   been omitted and filed separately with the Securities and Exchange
   Commission.
 
     (b) Financial Statement Schedules
 
     All schedules have been omitted because they are not required or because
the required information is given in the Company's Financial Statements or Notes
thereto.

<PAGE>   1

                                                          DRAFT OF JULY 14, 1998



                                3,100,000 Shares



                                  Common Stock

                                ($.01 Par Value)


                             UNDERWRITING AGREEMENT



                                                                 _________, 1998



BT Alex. Brown Incorporated
Merrill Lynch, Pierce, Fenner & Smith Incorporated
Piper Jaffray Inc.
As Representatives of the
      Several Underwriters
c/o BT Alex. Brown Incorporated
One South Street
Baltimore, Maryland 21202

Ladies and Gentlemen:

     Aspect Medical Systems, Inc., a Delaware corporation (the "Company"),
proposes to sell to the several underwriters (the "Underwriters") named in
Schedule I hereto for whom you are acting as representatives (the
"Representatives") an aggregate of 3,100,000 shares of the Company's Common
Stock, $.01 par value per share (the "Firm Shares"). The respective amounts of
the Firm Shares to be so purchased by the several Underwriters are set forth
opposite their names in Schedule I hereto. The Company also proposes to sell at
the Underwriters' option an aggregate of up to 465,000 additional shares of the
Company's Common Stock (the "Option Shares") as set forth below.

     As the Representatives, you have advised the Company (a) that you are
authorized to enter into this Agreement on behalf of the several Underwriters,
and (b) that the several Underwriters are willing, acting severally and not
jointly, to purchase the numbers of Firm Shares set forth opposite their
respective names in Schedule I, plus their pro rata portion of the Option Shares
if you elect to exercise the over-allotment option in whole or in part for the
accounts of the several Underwriters. The Firm Shares and the Option 

<PAGE>   2

                                      -2-


Shares (to the extent the aforementioned option is exercised) are herein
collectively called the "Shares."

     In consideration of the mutual agreements contained herein and of the
interests of the parties in the transactions contemplated hereby, the parties
hereto agree as follows:

     1.   REPRESENTATIONS AND WARRANTIES OF THE COMPANY.

          The Company represents and warrants to each of the Underwriters as 
follows:

          (a) A registration statement on Form S-1 (File No. 333-57739) with 
respect to the Shares has been prepared by the Company in conformity with the
requirements of the Securities Act of 1933, as amended (the "Act"), and the
Rules and Regulations (the "Rules and Regulations") of the Securities and
Exchange Commission (the "Commission") thereunder and has been filed with the
Commission. Copies of such registration statement, including any amendments
thereto, the preliminary prospectuses (meeting the requirements of the Rules and
Regulations) contained therein and the exhibits, financial statements and
schedules, as finally amended and revised, have heretofore been delivered by the
Company to you and, to the extent applicable, were identical in all material
respects to the electronically transmitted copies thereof filed with the
Commission pursuant to the Commission's Electronic Data Gathering, Analysis and
Retrieval System ("EDGAR"), except to the extent permitted by Regulation S-T.
Such registration statement, together with any registration statement filed by
the Company pursuant to Rule 462 (b) of the Act, collectively herein referred to
as the "Registration Statement," which shall be deemed to include all
information omitted therefrom in reliance upon Rule 430A promulgated under the
Act and contained in the Prospectus referred to below, has become effective
under the Act and no post-effective amendment to the Registration Statement has
been filed as of the date of this Agreement. "Prospectus" means the form of
prospectus first filed with the Commission pursuant to Rule 424(b) promulgated
under the Act. Each preliminary prospectus included in the Registration
Statement prior to the time it becomes effective is herein referred to as a
"Preliminary Prospectus." For purposes of this Agreement, all references to the
Registration Statement, any Preliminary Prospectus, the Prospectus, or any
amendment or supplement to any of the foregoing, shall be deemed to include the
respective copies thereof filed with the Commission pursuant to EDGAR.

          (b) The Company has been duly organized and is validly existing as a
corporation in good standing under the laws of the State of Delaware, with
corporate power and authority to own or lease its properties and conduct its
business as described in the Registration Statement. The Company is duly
qualified to transact business in all jurisdictions in which the conduct of its
business requires such qualification, except with a failure to be so qualified
would not have a material adverse effect on the business, financial condition,
liquidity or results of operations of the Company. The Company has no
subsidiaries.

<PAGE>   3
                                      -3-



          (c) The outstanding shares of Common Stock of the Company have been 
duly authorized and validly issued and are fully paid and non-assessable; the
Shares to be issued and sold by the Company have been duly authorized and when
issued and paid for as contemplated herein will be validly issued, fully paid
and non-assessable; and no preemptive rights of stockholders exist pursuant to
the Company's charter, bylaws or any other agreement or instrument to which the
Company is a party or any act taken by the Company or its officers and directors
with respect to any of the Shares or the issue and sale thereof. Neither the
filing of the Registration Statement nor the offering or sale of the Shares as
contemplated by this Agreement gives rise to any rights, other than those which
have been waived or satisfied, for or relating to the registration of any shares
of Common Stock.

          (d) The information set forth under the caption "Capitalization" in 
the Prospectus is true and correct. All of the Shares conform or when issued,
delivered and paid for in the manner set forth in this Agreement will conform to
the description thereof contained in the Prospectus. The form of certificates
for the Shares conforms to the corporate law of the jurisdiction of the
Company's incorporation.

          (e) The Commission has not issued an order preventing or suspending 
the use of any Prospectus relating to the proposed offering of the Shares nor
instituted proceedings for that purpose. The Registration Statement contains,
and the Prospectus and any amendments or supplements thereto will contain, all
statements which are required to be stated therein by, and will conform in all
material respects to, the requirements of the Act and the Rules and Regulations.
The Registration Statement and any amendment thereto do not contain, and will
not contain, any untrue statement of a material fact and do not omit, and will
not omit, to state any material fact required to be stated therein or necessary
to make the statements therein not misleading. The Prospectus and any amendments
and supplements thereto do not contain, and will not contain, any untrue
statement of material fact; and do not omit, and will not omit, to state any
material fact required to be stated therein or necessary to make the statements
therein, in the light of the circumstances under which they were made, not
misleading; provided, however, that the Company makes no representations or
warranties as to information contained in or omitted from the Registration
Statement or the Prospectus, or any such amendment or supplement, in reliance
upon, and in conformity with, written information furnished to the Company by or
on behalf of any Underwriter through the Representatives, specifically for use
in the preparation thereof.

          (f) The financial statements of the Company, together with related 
notes and schedules as set forth in the Registration Statement, present fairly
in all material respects the financial position and the results of operations
and cash flows of the Company, at the indicated dates and for the indicated
periods. Such financial statements and related schedules have been prepared in
accordance with generally accepted principles of accounting, consistently
applied throughout the periods involved, except as disclosed therein, and all
adjustments necessary for a fair presentation of results for such periods have
been made. The summary financial and statistical data included in the
Registration Statement presents fairly in all material respects the information
shown 

<PAGE>   4

                                      -4-


therein and such data has been compiled on a basis consistent with the financial
statements presented therein and the books and records of the Company.

          (g) Arthur Andersen LLP and Price Waterhouse, LLP, who have each 
certified certain of the financial statements filed with the Commission as part
of the Registration Statement, are each independent public accountants as
required by the Act and the Rules and Regulations.

          (h) There is no action, suit, claim or proceeding pending or, to the
knowledge of the Company, threatened against the Company before any court or
administrative agency or otherwise which if determined adversely to the Company
might result in any material adverse change in the earnings, business,
management, properties, assets, rights, operations, condition (financial or
otherwise) or prospects of the Company or to prevent the consummation of the
transactions contemplated hereby.

          (i) Except as described in the Prospectus, the Company has good and 
valid title to all of the properties and assets reflected in the financial
statements (or as described in the Registration Statement, including, without
limitations, intellectual property rights) hereinabove described, subject to no
lien, mortgage, pledge, charge or encumbrance of any kind except those reflected
in such financial statements (or as described in the Registration Statement) or
which are not material in amount. The Company occupies its leased properties
under valid and binding leases conforming in all material respects to the
description thereof set forth in the Registration Statement.

          (j) The Company has filed all Federal, State, local and foreign tax 
returns which have been required to be filed and has paid all taxes indicated by
said returns and all assessments received by it to the extent that such taxes
have become due, except for assessments being contested in good faith and for
which an adequate reserve for accrual has been established in accordance with
generally accepted accounting principles. All tax liabilities have been
adequately provided for in the financial statements of the Company, and the
Company does not know of any actual or proposed additional material tax
assessments.

          (k) Since the respective dates as of which information is given in the
Registration Statement, as it may be amended or supplemented, there has not been
any material adverse change or any development involving a prospective material
adverse change in or affecting the earnings, business, management, properties,
assets, rights, operations, condition (financial or otherwise), or business
prospects of the Company, whether or not occurring in the ordinary course of
business, and there has not been any material transaction entered into or any
material transaction that is probable of being entered into by the Company,
other than transactions in the ordinary course of business and changes and
transactions described in the Registration Statement, as it may be amended or
supplemented. The Company has no material contingent obligations which are not
disclosed in the Company's financial statements which are included in the
Registration Statement.

<PAGE>   5

                                      -5-


          (l) The Company is not, nor with the giving of notice or lapse of time
or both, will be, in violation of or in default under its Charter or By-Laws or
under any agreement, lease, contract, indenture or other instrument or
obligation to which it is a party or by which it, or any of its properties, is
bound and which default is of material significance in respect of the condition,
financial or otherwise of the Company or the business, management, properties,
assets, rights, operations, condition (financial or otherwise) or prospects of
the Company. The execution and delivery of this Agreement and the consummation
of the transactions herein contemplated and the fulfillment of the terms hereof
will not conflict with or result in a breach of any of the terms or provisions
of, or constitute a default under, any indenture, mortgage, deed of trust or
other agreement or instrument to which the Company is a party, or of the Charter
or By-Laws of the Company or any order, rule or regulation applicable to the
Company of any court or of any regulatory body or administrative agency or other
governmental body having jurisdiction.

          (m) Each approval, consent, order, authorization, designation, 
declaration or filing by or with any regulatory, administrative or other
governmental body necessary in connection with the execution and delivery by the
Company of this Agreement and the consummation by the Company of the
transactions herein contemplated (except such additional steps as may be
required by the National Association of Securities Dealers, Inc. (the "NASD") or
by the Nasdaq National Market or such additional steps as may be necessary to
qualify the Shares for public offering by the Underwriters under state
securities or Blue Sky laws) has been obtained or made and is in full force and
effect.

          (n) The Company holds, and is operating in compliance with, all 
licenses, certificates and permits from governmental authorities which are
material to the conduct of its business.

          (o) Neither the Company, nor to the Company's knowledge, any of its
affiliates, has taken or may take, directly or indirectly, any action designed
to cause or result in, or which has constituted or which might reasonably be
expected to constitute, the stabilization or manipulation of the price of the
shares of Common Stock to facilitate the sale or resale of the Shares.

          (p) The Company is not an "investment company" within the meaning of 
such term under the Investment Company Act of 1940 (as amended, the "1940 Act"),
and the rules and regulations of the Commission thereunder.

          (q) The Company maintains a system of internal accounting controls
sufficient to provide reasonable assurances that (i) transactions are executed
in accordance with management's general or specific authorization; (ii)
transactions are recorded as necessary to permit preparation of financial
statements in conformity with generally accepted accounting principles and to
maintain accountability for assets; (iii) access to assets is permitted only in
accordance with management's general or specific authorization; and (iv) the
recorded accountability for assets is compared with existing 

<PAGE>   6

                                      -6-


assets at reasonable intervals and appropriate action is taken with respect to
any differences.

          (r) The Company carries, or is covered by, insurance in such amounts 
and covering such risks as is adequate for the conduct of its business and the
value of its properties and as is customary for companies engaged in similar
industries.

          (s) The Company is in compliance in all material respects with all
presently applicable provisions of the Employee Retirement Income Security Act
of 1974, as amended, including the regulations and published interpretations
thereunder ("ERISA"); no "reportable event" (as defined in ERISA) has occurred
with respect to any "pension plan" (as defined in ERISA) for which the Company
would have any liability; the Company has not incurred and does not expect to
incur liability under (i) Title IV of ERISA with respect to termination of, or
withdrawal from, any "pension plan" or (ii) Sections 412 or 4971 of the Internal
Revenue Code of 1986, as amended, including the regulations and published
interpretations thereunder (the "Code"); and each "pension plan" for which the
Company would have any liability that is intended to be qualified under Section
401(a) of the Code is so qualified in all material respects and nothing has
occurred, whether by action or by failure to act, which would cause the loss of
such qualification.

          (t) The Company owns or possesses adequate licenses or other rights to
use all patents, patent applications, patent rights, inventions, trade secrets,
know-how, manufacturing processes, formulae, trademarks, trademark applications,
service marks, service mark applications, trade names, copyrights or other
information (collectively, "Intellectual Property") which the Company believes
are necessary to conduct its business as now conducted by it as described in the
Registration Statement and Prospectus; the Company has not received any notice
of, and has no knowledge of, any infringement of or conflict with asserted
rights of the Company by others with respect to any Intellectual Property except
as disclosed in the Prospectus; the Company has not received any notice of, and
has no knowledge of, any infringement of or conflict with asserted rights of
others with respect to any Intellectual Property, except as disclosed in the
Prospectus; to the knowledge of the Company, none of the patents owned or
licensed by the Company are unenforceable or invalid; the Company is not aware
of any U.S. or foreign patent applications of others which, if issued in the
form available to the Company, would preclude or limit the Company in its
business as now conducted or proposed to be conducted as described in the
Prospectus. The Company has duly and properly filed or caused to be filed with
the United States Patent and Trademark Office (the "PTO") and applicable foreign
and international patent authorities all patent applications described or
referred to in the Prospectus, and believes it has complied with the PTO's duty
of candor and disclosure for each of the United States patent applications
described or referred to in the Prospectus; the Company is unaware of any facts
which would preclude the grant of a patent from each of the patent applications
described or referred to in the Prospectus; the Company has no knowledge of any
facts which would preclude it from having clear title to its patent applications
referenced in the Prospectus; and the Company has not terminated or breached and
is not in violation of any agreement 

<PAGE>   7

                                      -7-



covering its Intellectual Property rights. Except as a result of the license of
its software in the ordinary course of its business, the Company is not aware of
the granting of any patents to third parties or the filing of patent
applications by third parties or any other rights of third parties to any of the
Company's Intellectual Property.

          (u) The Company owns all right, title and interest or has the 
requisite license in the products sold by the Company, and neither the products
sold by the Company nor any related documentation or materials are unlicensed
copies or are unauthorized derivative works of other code, designs or documents
owned, in whole or in part, by any third party, and further, all work performed
was original work performed only by persons under obligation to assign any
individual right, title and interest to the Company.

          (v) To the Company's knowledge, there are no affiliations or 
associations between any member of the NASD and any of the Company's officers,
directors or 5% or greater securityholders, except as previously disclosed to
you in writing.

     2.   PURCHASE, SALE AND DELIVERY OF THE FIRM SHARES.

          (a) On the basis of the representations, warranties and covenants 
herein contained, and subject to the conditions herein set forth, the Company
agrees to sell to the Underwriters and each Underwriter agrees, severally and
not jointly, to purchase, at a price of $_____ per share, the number of Firm
Shares set forth opposite the name of each Underwriter in Schedule I hereof,
subject to adjustments in accordance with Section 9 hereof.

          (b) Payment for the Firm Shares to be sold hereunder is to be made by 
wire transfer in Federal (same day) funds to an account designated by the
Company against delivery of certificates therefor through the facilities of the
Depository Trust Company, New York, New York at 10:00 a.m., New York time, on
the third business day after the date of this Agreement or at such other time
and date not later than five business days thereafter as you and the Company
shall agree upon, such time and date being herein referred to as the "Closing
Date." (As used herein, "business day" means a day on which the New York Stock
Exchange is open for trading and on which banks in New York are open for
business and are not permitted by law or executive order to be closed.)

          (c) In addition, on the basis of the representations and warranties 
herein contained and subject to the terms and conditions herein set forth, the
Company hereby grants an option to the several Underwriters to purchase the
Option Shares at the price per share as set forth in the first paragraph of this
Section 2. The option granted hereby may be exercised in whole or in part by
giving written notice (i) at any time before the Closing Date and (ii) only once
thereafter within 30 days after the date of this Agreement, by you, as
Representatives of the several Underwriters, to the Company setting forth the
number of Option Shares as to which the several Underwriters are exercising the
option, the names and denominations in which the Option Shares are to be
registered and the time and date at which such certificates are to be delivered.
The time and date at which 

<PAGE>   8

                                      -8-


certificates for Option Shares are to be delivered shall be determined by the
Representatives but shall not be earlier than three nor later than 10 full
business days after the exercise of such option, nor in any event prior to the
Closing Date (such time and date being herein referred to as the "Option Closing
Date"). If the date of exercise of the option is three or more days before the
Closing Date, the notice of exercise shall set the Closing Date as the Option
Closing Date. The number of Option Shares to be purchased by each Underwriter
shall be in the same proportion to the total number of Option Shares being
purchased as the number of Firm Shares being purchased by such Underwriter bears
to the total number of Firm Shares, adjusted by you in such manner as to avoid
fractional shares. The option with respect to the Option Shares granted
hereunder may be exercised only to cover over-allotments in the sale of the Firm
Shares by the Underwriters. You, as Representatives of the several Underwriters,
may cancel such option at any time prior to its expiration by giving written
notice of such cancellation to the Company. To the extent, if any, that the
option is exercised, payment for the Option Shares shall be made on the Option
Closing Date by wire transfer in Federal (same day) funds to an account
designated by the Company against delivery of certificates therefor through the
facilities of the Depository Trust Company, New York, New York at 10:00 a.m.,
New York time.

     3.   OFFERING BY THE UNDERWRITERS.

          It is understood that the several Underwriters are to make a public
offering of the Firm Shares as soon as the Representatives deem it advisable to
do so. The Firm Shares are to be initially offered to the public at the initial
public offering price set forth in the Prospectus. The Representatives may from
time to time thereafter change the public offering price and other selling
terms. To the extent, if at all, that any Option Shares are purchased pursuant
to Section 2 hereof, the Underwriters will offer them to the public on the
foregoing terms.

          It is further understood that you will act as the Representatives for 
the Underwriters in the offering and sale of the Shares in accordance with a
Master Agreement Among Underwriters entered into by you and the several other
Underwriters.

     4.   COVENANTS OF THE COMPANY.

          The Company covenants and agrees with the several Underwriters that:

          (a) The Company will (A) use its best efforts to cause the 
Registration Statement to become effective or, if the procedure in Rule 430A of
the Rules and Regulations is followed, to prepare and timely file with the
Commission under Rule 424(b) of the Rules and Regulations a Prospectus in a form
approved by the Representatives containing information previously omitted at the
time of effectiveness of the Registration Statement in reliance on Rule 430A of
the Rules and Regulations and (B) not file any amendment to the Registration
Statement or supplement to the Prospectus of which the Representatives shall not
previously have been advised and furnished with a copy or to which the
Representatives shall have reasonably objected in writing or which 

<PAGE>   9

                                      -9-


is not in compliance with the Rules and Regulations. To the extent applicable,
the copies of the Registration Statement and each amendment thereto (including
all exhibits filed therewith), and any Preliminary Prospectus or Prospectus (in
each case, as amended or supplemented) furnished to the Underwriters will be
identical to the electronically transmitted copies thereof filed with the
Commission pursuant to EDGAR, except to the extent permitted by Regulation S-T.

          (b) The Company will advise the Representatives promptly (A) when the
Registration Statement or any post-effective amendment thereto shall have become
effective, (B) of receipt of any comments from the Commission, (C) of any
request of the Commission for amendment of the Registration Statement or for
supplement to the Prospectus or for any additional information, and (D) of the
issuance by the Commission of any stop order suspending the effectiveness of the
Registration Statement or the use of the Prospectus or of the institution of any
proceedings for that purpose. The Company will use its best efforts to prevent
the issuance of any such stop order preventing or suspending the use of the
Prospectus and to obtain as soon as possible the lifting thereof, if issued.

          (c) The Company will cooperate with the Representatives in endeavoring
to qualify the Shares for sale under the securities laws of such jurisdictions
as the Representatives may reasonably have designated in writing and will make
such applications, file such documents, and furnish such information as may be
reasonably required for that purpose, provided the Company shall not be required
to qualify as a foreign corporation or to file a general consent to service of
process in any jurisdiction where it is not now so qualified or required to file
such a consent. The Company will, from time to time, prepare and file such
statements, reports, and other documents, as are or may be required to continue
such qualifications in effect for so long a period as the Representatives may
reasonably request for distribution of the Shares.

          (d) The Company will deliver to, or upon the order of, the 
Representatives, from time to time, as many copies of any Preliminary Prospectus
as the Representatives may reasonably request. The Company will deliver to, or
upon the order of, the Representatives during the period when delivery of a
Prospectus is required under the Act, as many copies of the Prospectus in final
form, or as thereafter amended or supplemented, as the Representatives may
reasonably request. The Company will deliver to the Representatives at or before
the Closing Date, four signed copies of the Registration Statement and all
amendments thereto including all exhibits filed therewith, and will deliver to
the Representatives such number of copies of the Registration Statement
(including such number of copies of the exhibits filed therewith that may
reasonably be requested), and of all amendments thereto, as the Representatives
may reasonably request.

          (e) The Company will comply with the Act and the Rules and 
Regulations, and the Securities Exchange Act of 1934, as amended (the "Exchange
Act"), and the rules and regulations of the Commission thereunder, so as to
permit the completion of the distribution of the Shares as contemplated in this
Agreement and the 

<PAGE>   10

                                      -10-



Prospectus. If during the period in which a prospectus is required by law to be
delivered by an Underwriter or dealer, any event shall occur as a result of
which, in the judgment of the Company or in the reasonable opinion of the
Underwriters, it becomes necessary to amend or supplement the Prospectus in
order to make the statements therein, in the light of the circumstances existing
at the time the Prospectus is delivered to a purchaser, not misleading, or, if
it is necessary at any time to amend or supplement the Prospectus to comply with
any law, the Company promptly will prepare and file with the Commission an
appropriate amendment to the Registration Statement or supplement to the
Prospectus so that the Prospectus as so amended or supplemented will not, in the
light of the circumstances when it is so delivered, be misleading, or so that
the Prospectus will comply with the law.

          (f) The Company will make generally available to its security holders,
as soon as it is practicable to do so, but in any event not later than 15 months
after the effective date of the Registration Statement, an earnings statement
(which need not be audited) in reasonable detail, covering a period of at least
12 consecutive months beginning after the effective date of the Registration
Statement, which earnings statement shall satisfy the requirements of Section
11(a) of the Act and Rule 158 of the Rules and Regulations and will advise you
in writing when such statement has been so made available.

          (g) The Company will, for a period of five years from the Closing 
Date, deliver to the Representatives copies of annual reports and copies of all
other documents, reports and information furnished by the Company to its
stockholders or filed with any securities exchange pursuant to the requirements
of such exchange or with the Commission pursuant to the Act or the Exchange Act.
The Company will deliver to the Representatives similar reports with respect to
significant subsidiaries, as that term is defined in the Rules and Regulations,
which are not consolidated in the Company's financial statements. To the extent
applicable, such reports or documents shall be identical to the electronically
transmitted copies thereof filed with the Commission pursuant to EDGAR, except
to the extent permitted by Regulation S-T.

          (h) Prior to the Closing Date, the Company will furnish to the
Underwriters, as soon as they have been prepared by or are available to the
Company, a copy of any unaudited interim financial statements of the Company for
any period subsequent to the period covered by the most recent financial
statements appearing in the Registration Statement and the Prospectus.

          (i) No offering, sale, short sale or other disposition of any shares
of Common Stock of the Company or other securities convertible into or
exchangeable or exercisable for shares of Common Stock or derivative of Common
Stock (or agreement for such) will be made for a period of 180 days after the
date of this Agreement, directly or indirectly, by the Company otherwise than
hereunder or with the prior written consent of BT Alex. Brown & Sons
Incorporated, except that the Company may without such consent (A) grant options
to purchase and sell shares of Common Stock under its current stock option,
equity incentive and purchase plans, as described in the Prospectus (the

<PAGE>   11

                                      -11-


"Company Equity Plans"), (B) issue shares upon the exercise of options issued
pursuant to the Company Equity Plans; AND (C) ISSUE SHARES IN RESPECT OF THE
ACQUISITION BY THE COMPANY OF THE ASSETS OR CAPITAL STOCK OF ANOTHER PERSON OR
ENTITY SO LONG AS (I) THE COMPANY PROVIDES REASONABLE NOTICE TO BT ALEX. BROWN
INCORPORATED AND (II) THE SHARES SO ISSUED BY THE COMPANY MAY NOT BE RESOLD FOR
A PERIOD OF AT LEAST 180 DAYS AFTER THE DATE OF THIS AGREEMENT.

          (j) The Company will use its best efforts to list, subject to notice
of issuance, the Shares on the Nasdaq National Market.

          (k) The Company has caused each officer and director and certain
stockholders of the Company to furnish to you, on or prior to the date of this
agreement, a letter or letters (a "Lockup Agreement") covering an aggregate of
at least _________ shares of Common Stock (including any securities convertible
into Common Stock), in form and substance satisfactory to the Underwriters,
pursuant to which each such person has agreed for a period expiring 180 days
after the date of the Prospectus (the "Lockup Period") not to (A) offer to sell,
contract to sell, pledge, transfer, grant any option to purchase or otherwise
dispose of, directly or indirectly, any shares of Common Stock of the Company,
any options, rights or warrants to purchase any shares of capital stock of the
Company (including any stock appreciation right, or similar right with an
exercise or conversion privilege at a price related to, or derived from, the
market price of the Common Stock of the Company) or any securities convertible
into or exchangeable for shares of Common Stock of the Company owned directly by
such person, acquired by such person after the date of such Lockup Agreement, or
which may be deemed to be beneficially owned by such person pursuant to the
Rules and Regulations promulgated under the Act. provided, however, that each
such person may transfer shares of Common Stock or options to purchase shares of
Common Stock pursuant to a bona fide gift or gifts, by will or intestacy to such
person's immediate family members or to trusts for the benefit of such immediate
family members and as a distribution to partners, stockholders or members of
such person, in each case only if such transferee executes and delivers to BT
Alex. Brown Incorporated a Lockup Agreement in the same form and content, and
with the same expiration date, as the Lockup Agreement signed by such person, or
(B) engage in any hedging or other transaction which is designed to or
reasonably expected to lead to or result in a disposition of such persons shares
of Common Stock during the Lockup Period, even if such shares would be disposed
of by someone other than such person. Such prohibited hedging or other
transactions would include, without limitation, any short sale (whether or not
against the box) or any purchase, sale or grant of any right (including, without
limitation, any put or call option) with respect to any of such persons shares
of Common Stock or with respect to any security (other than a broad-based market
basket or index) that includes, relates to or derives any significant part of
its value from such shares. [The Company has also requested from certain
stockholders that such stockholders comply with their respective obligations
pursuant to Section ___ of the Third Amended and Restated Registration Rights
Agreement dated February __, 1998 by and between the Company and such
stockholders.]

<PAGE>   12

                                      -12-


          (l) The Company shall apply the net proceeds of its sale of the Shares
as set forth in the Prospectus and shall include such information with respect
thereto in its periodic reports filed pursuant to Sections 13(a) and 15(d) of
the Exchange Act to the extent required by Rule 463 under the Act.

          (m) The Company shall not invest, or otherwise use the proceeds
received by the Company from its sale of the Shares in such a manner as would
require the Company or any of its subsidiaries to register as an investment
company under the 1940 Act.

          (n) The Company will maintain a transfer agent and, if necessary under
the jurisdiction of incorporation of the Company, a registrar for the Common
Stock.

          (o) The Company will not take, directly or indirectly, any action
designed to cause or result in, or that has constituted or might reasonably be
expected to constitute, the stabilization or manipulation of the price of any
securities of the Company.

          (p) The Company shall not file or cause to become effective a
Registration Statement on Form S-8 relating to the shares of Common Stock
issuable under any such stock option plan or stock purchase plan until 180 days
after the date of this Agreement.

     5.   COSTS AND EXPENSES.

          The Company will pay all costs, expenses and fees incident to the
performance of the obligations of the Company under this Agreement, including,
without limiting the generality of the foregoing, the following: accounting fees
of the Company; the fees and disbursements of counsel for the Company; the cost
of printing and delivering to, or as requested by, the Underwriters copies of
the Registration Statement, Preliminary Prospectuses, the Prospectus, this
Agreement, the Underwriters' Selling Memorandum, the Underwriters' Invitation
Letter, the Listing Application, the Blue Sky Survey and any supplements or
amendments thereto; the filing fees of the Commission; the filing fees and
expenses (including legal fees and disbursements) incident to securing any
required review by the NASD of the terms of the sale of the Shares; the Listing
Fee of the Nasdaq National Market; and the expenses, including the reasonable
fees and disbursements of counsel for the Underwriters, incurred in connection
with the qualification of the Shares under State securities or Blue Sky laws.
The Company agrees to pay all costs and expenses of the Underwriters, including
the fees and disbursements of counsel for the Underwriters, incident to the
offer and sale of directed shares of the Common Stock by the Underwriters to
employees and persons having business relationships with the Company. The
Company shall not, however, be required to pay for any of the Underwriters
expenses (other than those related to qualification under NASD regulation and
State securities or Blue Sky laws) except that, if this Agreement shall not be
consummated because the conditions in Section 6 hereof are not satisfied, or
because this Agreement is terminated by the Representatives pursuant to
Section 11 hereof, or by reason of any failure, refusal or inability on the part
of the Company to perform any 

<PAGE>   13

                                      -13-



undertaking or satisfy any condition of this Agreement or to comply with any of
the terms hereof on its part to be performed, unless such failure to satisfy
said condition or to comply with said terms be due to the default or omission of
any Underwriter, then the Company shall reimburse the several Underwriters for
reasonable out-of-pocket expenses, including fees and disbursements of counsel,
reasonably incurred in connection with investigating, marketing and proposing to
market the Shares or in contemplation of performing their obligations hereunder;
but the Company shall not in any event be liable to any of the several
Underwriters for damages on account of loss of anticipated profits from the sale
by them of the Shares.

     6.   CONDITIONS TO OBLIGATIONS OF THE UNDERWRITERS.

          The several obligations of the Underwriters to purchase the Firm
Shares on the Closing Date and the Option Shares, if any, on the Option Closing
Date are subject to the accuracy, as of the Closing Date or the Option Closing
Date, as the case may be, of the representations and warranties of the Company
contained herein, and to the performance by the Company of its covenants and
obligations hereunder and to the following additional conditions:

          (a) The Registration Statement and all post-effective amendments
thereto shall have become effective and any and all filings required by Rule 424
and Rule 430A of the Rules and Regulations shall have been made, and any request
of the Commission for additional information (to be included in the Registration
Statement or otherwise) shall have been disclosed to the Representatives and
complied with to their reasonable satisfaction. No stop order suspending the
effectiveness of the Registration Statement, as amended from time to time, shall
have been issued and no proceedings for that purpose shall have been taken or,
to the knowledge of the Company, shall be contemplated by the Commission and no
injunction, restraining order, or order of any nature by a Federal or state
court of competent jurisdiction shall have been issued as of the Closing Date or
Option Closing Date, as the case may be, which would prevent the issuance of the
Shares.

          (b) The Representatives shall have received on the Closing Date or the
Option Closing Date, as the case may be, the opinion of Hale and Dorr, LLP,
counsel for the Company, dated the Closing Date or the Option Closing Date, as
the case may be, addressed to the Underwriters (and stating that it may be
relied upon by counsel to the Underwriters) to the effect that:

              (i)  The Company has been duly incorporated and is validly 
existing as a corporation in good standing under the laws of the State of
Delaware, with corporate power and authority to own or lease its properties and
conduct its business as described in the Registration Statement; to such
counsel's knowledge, the Company has no subsidiaries; and the Company is duly
qualified to transact business the Commonwealth of Massachusetts.

              (ii) The Company has authorized and outstanding capital stock as 
set forth under the caption "Capitalization" in the Prospectus (except for
issuances 

<PAGE>   14

                                      -14-


subsequent to __________ __, 1998 pursuant to the exercise of employee stock
options); the authorized shares of the Company's Common Stock have been duly
authorized; the outstanding shares of the Company's Common Stock have been duly
authorized and validly issued and are fully paid and non-assessable; all of the
Shares conform, or when issued, delivered and paid for in accordance with the
terms of the Agreement will conform, in all material respects, to the
description thereof contained in the Prospectus; the certificates evidencing the
Shares, assuming they are in the form filed with the Commission, are in due and
proper form under Delaware law; the shares of Common Stock, including the Option
Shares, if any, to be sold by the Company pursuant to this Agreement have been
duly authorized and will be validly issued, fully paid and non-assessable when
issued and paid for as contemplated by this Agreement; and no preemptive rights
of stockholders exist under Delaware law or the Company's Restated Certificate
of Incorporation (the "Charter") or its By-laws, each as amended to date, with
respect to any of the Shares or the issue or sale thereof and, to the knowledge
of such counsel, no contractual preemptive rights of stockholders exist with
respect to any of the Shares or the issue or sale thereof.

              (iii) Except as described in or contemplated by the Prospectus, to
the knowledge of such counsel, there are no outstanding securities of the
Company convertible or exchangeable into or evidencing the right to purchase or
subscribe for any shares of capital stock of the Company and there are no
outstanding or authorized options, warrants or rights of any character
obligating the Company to issue any shares of its capital stock or any
securities convertible or exchangeable into or evidencing the right to purchase
or subscribe for any shares of such stock; and except as described in the
Prospectus, to the knowledge of such counsel, no holder of any securities of the
Company or any other person has the right, contractual or otherwise, which has
not been satisfied or effectively waived, to cause the Company to sell or
otherwise issue to them, or to permit them to underwrite the sale of, any of the
Shares or the right to have any Shares or other securities of the Company
included in the Registration Statement or the right, as a result of the filing
of the Registration Statement, to require registration under the Act of any
shares of Common Stock or other securities of the Company.

              (iv)  The Registration Statement has become effective under the 
Act and, to the knowledge of such counsel, no stop order proceedings with
respect thereto have been instituted or are pending or threatened by the
Commission.

              (v)   The Registration Statement and each amendment thereto when 
filed and when declared effective, complied as to form in all material respects
with the requirements of the Act and the applicable Rules and Regulations
thereunder (except that such counsel need express no opinion as to the financial
statements, including the notes and schedules thereto, or any other financial,
statistical or accounting information, or information relating to the
Underwriters or the method of distribution of the Shares by the Underwriters,
included in the Registration Statement). The Prospectus and each supplement
thereto complies as to form in all material respects with the requirements of
the Act and the applicable Rules and Regulations thereunder (except that such
counsel need express no opinion as to the financial statements, including the
notes and schedules 

<PAGE>   15

                                      -15-


thereto, or any other financial, statistical or accounting information, or
information relating to the Underwriters or the method of distribution of the
Shares by the Underwriters, included in the Prospectus). In passing upon the
form of such documents, such counsel is not passing upon the statements made
therein and takes no responsibility therefor.

              (vi)   The statements under the captions "Risk Factors -- Shares
Eligible for Future Sale and Potential Adverse Effect on Market Price," "Risk
Factors -- Anti-Takeover Effect of Certain Charter and By-Law and Other
Provisions," "Risk Factors -- Dependence on Patents, Trademarks, Licenses and
Proprietary Rights," "Business -- Patents and Proprietary Rights," "Description
of Capital Stock" and "Shares Eligible for Future Sale" in the Prospectus,
insofar as such statements constitute a summary of documents referred to therein
or matters of law, fairly summarize in all material respects the information
called for with respect to such documents and matters.

              (vii)  Such counsel does not know of any contracts or documents
required by the Act or the Rules and Regulations to be filed as exhibits to the
Registration Statement or described in the Registration Statement or the
Prospectus which are not so filed or described as required, and such contracts
and documents as are summarized in the Registration Statement or the Prospectus
are fairly summarized in all material respects.

              (viii) Such counsel knows of no material legal or governmental
proceedings pending or threatened against the Company required to be described
on the Prospectus which are not described as required.

              (ix)   The execution and delivery of this Agreement by the Company
and the consummation by the Company of the transactions herein contemplated do
not conflict with or result in a breach of any of the terms or provisions of, or
constitute a default under, the Charter or By-Laws of the Company, or any
agreement or instrument to which the Company is a party and which is listed as
an exhibit to the Registration Statement.

              (x)    This Agreement has been duly authorized, executed and 
delivered by the Company.

              (xi)   No approval, consent, order, authorization, designation,
declaration or filing by or with any regulatory, administrative or other
governmental body is necessary in connection with the execution and delivery of
this Agreement by the Company and the consummation by the Company of the
transactions herein contemplated (other than as may be required by the NASD, the
Nasdaq National Market or as required by State securities and Blue Sky laws, as
to which such counsel need express no opinion) except such as have been obtained
or made.

              (xii)  The Company is not, and will not become, as a result of the
consummation of the transactions contemplated by this Agreement, and application
of the 

<PAGE>   16

                                      -16-


net proceeds therefrom as described in the Prospectus, required to register as
an investment company under the 1940 Act.

              (xiii) The Company holds eight United States patents and ______
foreign patents, has filed four additional United States patent applications and
_____ patent applications in certain foreign countries, as listed in a schedule
to the opinion, and has licensed another United States patent from a third
party. In addition, the Company holds one United States trademark registration
and ______ foreign trademark registrations, has filed ____ United States
trademark applications and ___ trademark applications in certain foreign
countries, as listed in schedule to the opinion, and has licensed another United
States trademark registration from a third party.

              (xiv)  Such counsel knows of no facts which would result in any 
third party possessing any ownership right in any of to the Company's patents
and patent applications referred to or described in the Registration Statement
and Prospectus, or a valid license to the patents and patent applications
licensed from third parties referred to or described in the Registration
Statement and Prospectus. To the knowledge of such counsel, the Company and each
licensor has complied with the Patent and Trademark Office ("PTO") duty of
candor and good faith in dealing with the PTO, including the duty to disclose to
the PTO all information known to be material to the patentability of each of
such United States patents and patent applications. To the knowledge of such
counsel, all assignments from each named inventor to, as the case may be, the
Company or Licensor, have been executed and recorded with the PTO for each
patent and patent application. Such counsel is not aware of any pending U.S. or
foreign patent applications which, if issued, would limit or prohibit the
business now conducted or proposed to be conducted by the Company as described
in the Registration Statement and the Prospectus, except as described therein.
Such counsel is not aware of any patents of others which are or would be
infringed by specific products or processes referred to in the Registration
Statement and Prospectus in such manner as to materially and adversely affect
the Company, except as described therein.

              (xv)   To such counsel's knowledge, there are no legal or 
governmental proceedings pending relating to the Intellectual Property or ,
other than PTO review of pending applications for patents, including appeal
proceedings, and, to such counsel's knowledge, no such proceedings are
threatened or contemplated by governmental authorities or others.

          In rendering such opinion Hale and Dorr LLP may rely as to all matters
governed other than by the state law of the Commonwealth of Massachusetts, the
Delaware General Corporation Law statute or Federal laws on local counsel in
such jurisdictions, provided that in each case Hale and Dorr LLP shall state
that they believe that they and the Underwriters are justified in relying on
such other counsel. In addition to the matters set forth above, such opinion
shall also include a statement to the effect that nothing has come to the
attention of such counsel which leads them to believe that (i) the Registration
Statement, at the time it became effective under the Act (but after giving
effect to any modifications incorporated therein pursuant to Rule 430A under the
Act) 

<PAGE>   17

                                      -17-


contained an untrue statement of a material fact or omitted to state a material
fact required to be stated therein or necessary to make the statements therein
not misleading, and (ii) the Prospectus, or any supplement thereto, on the date
it was filed pursuant to the Rules and Regulations and as of the Closing Date or
the Option Closing Date, as the case may be, contained an untrue statement of a
material fact or omitted to state a material fact necessary in order to make the
statements therein, in the light of the circumstances under which they are made,
not misleading (except that such counsel need express no view as to financial
statements; including the notes and schedules thereto, or any other financial,
statistical or accounting information, or information relating to the
Underwriters or the method of distribution of the Shares by the Underwriters,
included therein). With respect to such statement, Hale and Dorr LLP may state
that their belief is based upon the procedures set forth therein, but is without
independent check and verification.

          (c) You shall have received on the Closing Date or the Option Closing
Date, as the case may be, the following opinion of Covington and Burling,
special FDA regulatory counsel to Company, dated the Closing Date or Option
Closing Date, as the case may be, addressed to the Underwriters (and stating
that it may be relied upon by counsel to the Underwriters), to the effect that
they serve as special FDA regulatory counsel to the Company and that:

              (i)   The statements in the Registration Statement and Prospectus 
under the captions "Risk Factors -- Government Regulation" and "Business --
Government Regulation," insofar as such statements purport to summarize
applicable provisions of the Federal Food, Drug and Cosmetic Act, as amended,
and the regulations promulgated thereunder, are accurate in all material
respects. 

              (ii) Such counsel is of the opinion that the statements under the
caption "Business -- Government Regulation," insofar as such statements purport
to summarize applicable European regulatory requirements for medical device
products, are accurate in all material respects.

              (iii) Based solely on oral representations made to such counsel 
by officers of the Company and a review of certain regulatory documents made
available by the Company, such counsel is not aware of any adverse judgment,
injunction, decree or order that has been issued by the FDA or brought by or on
behalf of the FDA against the Company, or any action, proceeding or
investigation pending before the FDA, or threatened by the FDA, against the
Company.

               (iv) Based solely on the description of the Company's business 
and products set forth in the Prospectus, and on oral representations made to
such counsel by certain officers of the Company concerning certain conversations
and meetings held by the Company with FDA reviewers to discuss the applicable
regulatory requirements for those products (in which we did not participate),
and with the exception of certain modifications to approved products for which
the Company has independently determined that additional approvals are not
required, the Company has obtained all product approvals from the FDA for its
currently marketed products described in the Prospectus.

<PAGE>   18

                                      -18-


     In rendering the foregoing opinion, such counsel may state that they have 
not independently verified nor do they take any responsibility for nor are
they addressing in any way any statements of fact, any statements concerning
foreign law or any legal conclusions or statements of belief attributable to the
Company or whether or not the Company is in compliance with applicable FDA
regulations.

     In addition to the foregoing opinions, counsel shall state that:

     During the course of preparation of the Registration Statement, such 
counsel participated in certain discussions with officers of the Company as to
the FDA regulatory matters dealt with under the captions "Risk Factors -
Government Regulation" and "Business -Government Regulation" in the Prospectus.
While such counsel has not undertaken to determine independently and such
counsel does not assume any responsibility for, the accuracy, completeness, or
fairness of the statements under such captions in the Prospectus, such counsel
shall state on the basis of these discussions that no facts have come to their
attention which cause them to believe that the statements in the Prospectus
under the captions "Risk Factors - Government Regulation" and Business -
Government Regulation," insofar as such statements relate to FDA regulatory
matters, at the time the Registration Statement became effective, contained an
untrue statement of a material fact or omitted to state a material fact required
to be stated therein or necessary to make the statements therein not misleading,
or at the Closing Date or the Option Closing Date, as the case may be, contains
an untrue statement of a material fact or omits to state a material fact
necessary in order to make the statements therein, in the light of the
circumstances under which they were made, not misleading.

          (d) The Representatives shall have received from Testa, Hurwitz &
Thibeault, LLP, counsel for the Underwriters, an opinion dated the Closing Date
or the Option Closing Date, as the case may be, substantially to the effect
specified in subparagraphs (ii), (iii), (iv) (ix) and (xi) of Paragraph (b) of
this Section 6, and that the Company is a duly organized and validly existing
corporation under the laws of the State of Delaware. In rendering such opinion
Testa, Hurwitz & Thibeault, LLP may rely as to all matters governed other than
by the laws of the State of Delaware or Federal laws on the opinion of counsel
referred to in Paragraph (b) of this Section 6. In addition to the matters set
forth above, such opinion shall also include a statement to the effect that
nothing has come to the attention of such counsel which leads them to believe
that (i) the Registration Statement, or any amendment thereto, as of the time it
became effective under the Act (but after giving effect to any modifications
incorporated therein pursuant to Rule 430A under the Act) as of the Closing Date
or the Option Closing Date, as the case may be, contained an untrue statement of
a material fact or omitted to state a material fact required to be stated
therein or necessary to make the statements therein not misleading, and (ii) the
Prospectus, or any supplement thereto, on the date it was filed pursuant to the
Rules and Regulations and as of the Closing Date or the Option Closing Date, as
the case may be, contained an untrue statement of a material fact or omitted to
state a material fact, necessary in order to make the statements therein, in the
light of the circumstances under which they are made, not misleading (except
that such counsel need 

<PAGE>   19

                                      -19-


express no view as to financial statements, schedules and statistical
information therein). With respect to such statement, Testa, Hurwitz &
Thibeault, LLP may state that their belief is based upon the procedures set
forth therein, but is without independent check and verification.

          (e) The Representatives shall have received at or prior to the Closing
Date from Testa, Hurwitz & Thibeault LLP a memorandum or summary, in form and
substance satisfactory to the Representatives, with respect to the qualification
for offering and sale by the Underwriters of the Shares under the State
securities or Blue Sky laws of such jurisdictions as the Representatives may
reasonably have designated to the Company.

          (f) You shall have received, on each of the date hereof, the Closing
Date and the Option Closing Date, as the case may be, a letter dated the date
hereof, the Closing Date or the Option Closing Date, as the case may be, in form
and substance satisfactory to you, from each of Arthur Andersen LLP and Price
Waterhouse LLP confirming that they are each independent public accountants
within the meaning of the Act and the applicable published Rules and Regulations
thereunder and stating that in each of their opinions the financial statements
and schedules examined by them and included in the Registration Statement comply
in form in all material respects with the applicable accounting requirements of
the Act and the related published Rules and Regulations; and containing such
other statements and information as is ordinarily included in accountants'
"comfort letters" to Underwriters with respect to the financial statements and
certain financial and statistical information contained in the Registration
Statement and Prospectus.

          (g) The Representatives shall have received on the Closing Date or the
Option Closing Date, as the case may be, a certificate or certificates of the
Chief Executive Officer and the Chief Financial Officer of the Company to the
effect that, as of the Closing Date or the Option Closing Date, as the case may
be:

              (i)   The Registration Statement has become effective under the 
Act and no stop order suspending the effectiveness of the Registrations
Statement has been issued, and no proceedings for such purpose have been taken
or are, to his knowledge, contemplated by the Commission;

              (ii)  The representations and warranties of the Company contained 
in Section 1 hereof are true and correct as of the Closing Date or the Option
Closing Date, as the case may be;

              (iii) All filings required to have been made pursuant to Rules 424
or 430A under the Act have been made;

              (iv)  He has carefully examined the Registration Statement and the
Prospectus and, in his opinion, as of the effective date of the Registration
Statement, the statements contained in the Registration Statement were true and
correct in all material 

<PAGE>   20

                                      -20-


respects, and such Registration Statement and Prospectus did not omit to state a
material fact required to be stated therein or necessary in order to make the
statements therein not misleading, and since the effective date of the
Registration Statement, no event has occurred which should have been set forth
in a supplement to or an amendment of the Prospectus which has not been so set
forth in such supplement or amendment; and

              (v)  Since the respective dates as of which information is given 
in the Registration Statement and Prospectus, there has not been any material
adverse change or any development involving a prospective material adverse
change in or affecting the condition, financial or otherwise, of the Company or
the earnings, business, management, properties, assets, rights, operations,
condition (financial or otherwise) or business prospects of the Company, whether
or not arising in the ordinary course of business.

          (h) The Company shall have furnished to the Representatives such
further certificates and documents confirming the representations and
warranties, covenants and conditions contained herein and related matters as the
Representatives may reasonably have requested.

          (i) The Firm Shares and Option Shares, if any, have been approved for
designation upon notice of issuance on the Nasdaq National Market.

          (j) The Lockup Agreements described in Section 4 (k) are in full force
and effect.

          The opinions and certificates mentioned in this Agreement shall be
deemed to be in compliance with the provisions hereof only if they are in all
material respects satisfactory to the Representatives and to Testa, Hurwitz &
Thibeault, LLP, counsel for the Underwriters.

          If any of the conditions hereinabove provided for in this Section 6
shall not have been fulfilled when and as required by this Agreement to be
fulfilled, the obligations of the Underwriters hereunder may be terminated by
the Representatives by notifying the Company of such termination in writing or
by telegram at or prior to the Closing Date or the Option Closing Date, as the
case may be.

          In such event, the Company and the Underwriters shall not be under any
obligation to each other (except to the extent provided in Sections 5 and 8
hereof).

     7.   CONDITIONS OF THE OBLIGATIONS OF THE COMPANY.

     The obligations of the Company to sell and deliver the portion of the 
Shares required to be delivered as and when specified in this Agreement are
subject to the conditions that at the Closing Date or the Option Closing Date,
as the case may be, no stop order suspending the effectiveness of the
Registration Statement shall have been issued and in effect or proceedings
therefor initiated or threatened.

<PAGE>   21

                                      -21-


     8.   INDEMNIFICATION.

               (a) The Company agrees:

                    (1) to indemnify and hold harmless each Underwriter and each
person, if any, who controls any Underwriter within the meaning of the Act,
against any losses, claims, damages or liabilities to which such Underwriter or
any such controlling person may become subject under the Act or otherwise,
insofar as such losses, claims, damages or liabilities (or actions or
proceedings in respect thereof) arise out of or are based upon (i) any untrue
statement or alleged untrue statement of any material fact contained in the
Registration Statement, any Preliminary Prospectus, the Prospectus or any
amendment or supplement thereto, (ii) the omission or alleged omission to state
therein a material fact required to be stated therein or necessary to make the
statements therein not misleading, or (iii) any act or failure to act by any
Underwriter in connection with, or relating in any manner to, the Shares or the
offering contemplated hereby, and which is included as part of or referred to in
any loss, claim, damage, liability or action arising out of or based upon
matters covered by clause (i) or (ii) above (provided, that the Company shall
not be liable under this clause (iii) to the extent that it is determined in a
final judgment by a court of competent jurisdiction that such loss, claim,
damage, liability or action resulted directly from any such acts or failures to
act undertaken or omitted to be taken by such Underwriter through its gross
negligence or willful misconduct); provided, however, that the Company will not
be liable in any such case to the extent that any such loss, claim, damage or
liability arises out of or is based upon an untrue statement or alleged untrue
statement, or omission or alleged omission made in the Registration Statement,
any Preliminary Prospectus, the Prospectus, or such amendment or supplement, in
reliance upon and in conformity with written information furnished to the
Company by or through the Representatives specifically for use in the
preparation thereof; and provided further, that Company shall not be liable to
any Underwriter under this Section 8(a) with respect to any untrue statements of
a material fact contained in, or the omission of a material fact from, any
Preliminary Prospectus which untrue statement or omission was corrected in the
Prospectus, if such Underwriter sold Shares to the person alleging such loss,
claim, damage or liability without sending or giving, at or prior to the written
confirmation of such sale, a copy of the Prospectus if the Company has
previously furnished copies thereof to such Underwriter.

                    (2) to reimburse each Underwriter and each such controlling
person upon demand for any legal or other out-of-pocket expenses reasonably
incurred by such Underwriter or such controlling person in connection with
investigating or defending any such loss, claim, damage or liability, action or
proceeding or in responding to a subpoena or governmental inquiry related to the
offering of the Shares, whether or not such Underwriter or controlling person is
a party to any action or proceeding. In the event that it is finally judicially
determined that the Underwriters were not entitled to receive payments for legal
and other expenses pursuant to this subparagraph, the Underwriters will promptly
return all sums that had been advanced pursuant hereto.

<PAGE>   22

                                      -22-


          (b) Each Underwriter severally and not jointly will indemnify and hold
harmless the Company, each of its directors, each of its officers who have
signed the Registration Statement and each person, if any, who controls the
Company within the meaning of the Act, against any losses, claims, damages or
liabilities to which the Company or any such director, officer, or controlling
person may become subject under the Act or otherwise, insofar as such losses,
claims, damages or liabilities (or actions or proceedings in respect thereof)
arise out of or are based upon (i) any untrue statement or alleged untrue
statement of any material fact contained in the Registration Statement, any
Preliminary Prospectus, the Prospectus or any amendment or supplement thereto,
or (ii) the omission or the alleged omission to state therein a material fact
required to be stated therein or necessary to make the statements therein not
misleading in the light of the circumstances under which they were made; and
will reimburse any legal or other expenses reasonably incurred by the Company or
any such director, officer, or controlling person in connection with
investigating or defending any such loss, claim, damage, liability, action or
proceeding; provided, however, that each Underwriter will be liable in each case
to the extent, but only to the extent, that such untrue statement or alleged
untrue statement or omission or alleged omission has been made in the
Registration Statement, any Preliminary Prospectus, the Prospectus or such
amendment or supplement, in reliance upon and in conformity with written
information furnished to the Company by or through the Representatives
specifically for use in the preparation thereof. This indemnity agreement will
be in addition to any liability which such Underwriter may otherwise have.

          (c) In case any proceeding (including any governmental investigation)
shall be instituted involving any person in respect of which indemnity may be
sought pursuant to this Section 8, such person (the "indemnified party") shall
promptly notify the person against whom such indemnity may be sought (the
"indemnifying party") in writing. No indemnification provided for in Section
8(a) or (b) shall be available to any party who shall fail to give notice as
provided in this Section 8(c) if the party to whom notice was not given was
unaware of the proceeding to which such notice would have related and was
materially prejudiced by the failure to give such notice, but the failure to
give such notice shall not relieve the indemnifying party or parties from any
liability which it or they may have to the indemnified party for contribution or
otherwise than on account of the provisions of Section 8(a) or (b). In case any
such proceeding shall be brought against any indemnified party and it shall
notify the indemnifying party of the commencement thereof, the indemnifying
party shall be entitled to participate therein and, to the extent that it shall
wish, jointly with any other indemnifying party similarly notified, to assume
the defense thereof, with counsel selected by such indemnifying party and
satisfactory to such indemnified party and shall pay as incurred the fees and
disbursements of such counsel related to such proceeding. In any such
proceeding, any indemnified party shall have the right to retain its own counsel
at its own expense. Notwithstanding the foregoing, the indemnifying party shall
pay as incurred (or within 30 days of presentation) the fees and expenses of the
counsel retained by the indemnified party in the event (i) the indemnifying
party and the indemnified party shall have mutually agreed to the retention of
such counsel, (ii) the named parties to any such proceeding (including any
impleaded parties) include both the indemnifying party and the 

<PAGE>   23

                                      -23-


indemnified party and representation of both parties by the same counsel would
be inappropriate due to actual or potential differing interests between them or
(iii) the indemnifying party shall have failed to assume the defense and employ
counsel acceptable to the indemnified party within a reasonable period of time
after notice of commencement of the action. It is understood that the
indemnifying party shall not, in connection with any proceeding or related
proceedings in the same jurisdiction, be liable for the reasonable fees and
expenses of more than one separate firm for all such indemnified parties. Such
firm shall be designated in writing by you in the case of parties indemnified
pursuant to Section 8(a) and by the Company in the case of parties indemnified
pursuant to Section 8(b). The indemnifying party shall not be liable for any
settlement of any proceeding effected without its written consent but if settled
with such consent or if there be a final judgment for the plaintiff, the
indemnifying party agrees to indemnify the indemnified party from and against
any loss or liability by reason of such settlement or judgment. In addition, the
indemnifying party will not, without the prior written consent of the
indemnified party, settle or compromise or consent to the entry of any judgment
in any pending or threatened claim, action or proceeding of which
indemnification may be sought hereunder (whether or not any indemnified party is
an actual or potential party to such claim, action or proceeding) unless such
settlement, compromise or consent includes an unconditional release of each
indemnified party from all liability arising out of such claim, action or
proceeding.

          (d) If the indemnification provided for in this Section 8 is
unavailable to or insufficient to hold harmless an indemnified party under
Section 8(a) or (b) above in respect of any losses, claims, damages or
liabilities (or actions or proceedings in respect thereof) referred to therein,
then each indemnifying party shall contribute to the amount paid or payable by
such indemnified party as a result of such losses, claims, damages or
liabilities (or actions or proceedings in respect thereof) in such proportion as
is appropriate to reflect the relative benefits received by the Company on the
one hand and the Underwriters on the other from the offering of the Shares. If,
however, the allocation provided by the immediately preceding sentence is not
permitted by applicable law then each indemnifying party shall contribute to
such amount paid or payable by such indemnified party in such proportion as is
appropriate to reflect not only such relative benefits but also the relative
fault of the Company on the one hand and the Underwriters on the other in
connection with the statements or omissions which resulted in such losses,
claims, damages or liabilities, (or actions or proceedings in respect thereof),
as well as any other relevant equitable considerations. The relative benefits
received by the Company on the one hand and the Underwriters on the other shall
be deemed to be in the same proportion as the total net proceeds from the
offering (before deducting expenses) received by the Company bear to the total
underwriting discounts and commissions received by the Underwriters, in each
case as set forth in the table on the cover page of the Prospectus. The relative
fault shall be determined by reference to, among other things, whether the
untrue or alleged untrue statement of a material fact or the omission or alleged
omission to state a material fact relates to information supplied by the Company
on the one hand or the Underwriters on the other and the parties' relative
intent, knowledge, access to information and opportunity to correct or prevent
such statement or omission.

<PAGE>   24

                                      -24-


          The Company and the Underwriters agree that it would not be just and
equitable if contributions pursuant to this Section 8(d) were determined by pro
rata allocation (even if the Underwriters were treated as one entity for such
purpose) or by any other method of allocation which does not take account of the
equitable considerations referred to above in this Section 8(d). The amount paid
or payable by an indemnified party as a result of the losses, claims, damages or
liabilities (or actions or proceedings in respect thereof) referred to above in
this Section 8(d) shall be deemed to include any legal or other expenses
reasonably incurred by such indemnified party in connection with investigating
or defending any such action or claim. Notwithstanding the provisions of this
subsection (d), (i) no Underwriter shall be required to contribute any amount in
excess of the underwriting discounts and commissions applicable to the Shares
purchased by such Underwriter and (ii) no person guilty of fraudulent
misrepresentation (within the meaning of Section 11(f) of the Act) shall be
entitled to contribution from any person who was not guilty of such fraudulent
misrepresentation. The Underwriters' obligations in this Section 8(d) to
contribute are several in proportion to their respective underwriting
obligations and not joint.

          (e) In any proceeding relating to the Registration Statement, any
Preliminary Prospectus, the Prospectus or any supplement or amendment thereto,
each party against whom contribution may be sought under this Section 8 hereby
consents to the jurisdiction of any court having jurisdiction over any other
contributing party, agrees that process issuing from such court may be served
upon him or it by any other contributing party and consents to the service of
such process and agrees that any other contributing party may join him or it as
an additional defendant in any such proceeding in which such other contributing
party is a party.

          (f) Any losses, claims, damages, liabilities or expenses for which an
indemnified party is entitled to indemnification or contribution under this
Section 8 shall be paid by the indemnifying party to the indemnified party as
such losses, claims, damages, liabilities or expenses are incurred. The
indemnity and contribution agreements contained in this Section 8 and the
representations and warranties of the Company set forth in this Agreement shall
remain operative and in full force and effect, regardless of (i) any
investigation made by or on behalf of any Underwriter or any person controlling
any Underwriter, the Company, its directors or officers or any persons
controlling the Company, (ii) acceptance of any Shares and payment therefor
hereunder, and (iii) any termination of this Agreement. A successor to any
Underwriter, or to the Company, its directors or officers, or any person
controlling the Company, shall be entitled to the benefits of the indemnity,
contribution and reimbursement agreements contained in this Section 8.

     9.   DEFAULT BY UNDERWRITERS.

          If on the Closing Date or the Option Closing Date, as the case may be,
any Underwriter shall fail to purchase and pay for the portion of the Shares
which such Underwriter has agreed to purchase and pay for on such date
(otherwise than by reason of 

<PAGE>   25

                                      -25-


any default on the part of the Company), you, as Representatives of the
Underwriters, shall use your reasonable efforts to procure within 36 hours
thereafter one or more of the other Underwriters, or any others, to purchase
from the Company such amounts as may be agreed upon and upon the terms set forth
herein, the Firm Shares or Option Shares, as the case may be, which the
defaulting Underwriter or Underwriters failed to purchase. If during such 36
hours you, as such Representatives, shall not have procured such other
Underwriters, or any others, to purchase the Firm Shares or Option Shares, as
the case may be, agreed to be purchased by the defaulting Underwriter or
Underwriters, then (a) if the aggregate number of shares with respect to which
such default shall occur does not exceed 10% of the Firm Shares or Option
Shares, as the case may be, covered hereby, the other Underwriters shall be
obligated, severally, in proportion to the respective numbers of Firm Shares or
Option Shares, as the case may be, which they are obligated to purchase
hereunder, to purchase the Firm Shares or Option Shares, as the case may be,
which such defaulting Underwriter or Underwriters failed to purchase, or (b) if
the aggregate number of shares of Firm Shares or Option Shares, as the case may
be, with respect to which such default shall occur exceeds 10% of the Firm
Shares or Option Shares, as the case may be, covered hereby, the Company or you
as the Representatives of the Underwriters will have the right, by written
notice given within the next 36-hour period to the parties to this Agreement, to
terminate this Agreement without liability on the part of the non-defaulting
Underwriters or of the Company except to the extent provided in Section 8
hereof. In the event of a default by any Underwriter or Underwriters, as set
forth in this Section 9, the Closing Date or Option Closing Date, as the case
may be, may be postponed for such period, not exceeding seven days, as you, as
Representatives, may determine in order that the required changes in the
Registration Statement or in the Prospectus or in any other documents or
arrangements may be effected. The term "Underwriter" includes any person
substituted for a defaulting Underwriter. Any action taken under this Section 9
shall not relieve any defaulting Underwriter from liability in respect of any
default of such Underwriter under this Agreement.

     10.  NOTICES.

          All communications hereunder shall be in writing and, except as
otherwise provided herein, will be mailed, delivered, telecopied or telegraphed
and confirmed as follows: if to the Underwriters, to BT Alex. Brown
Incorporated, One South Street, Baltimore, Maryland 21202, Attention: Russell T.
Ray; with a copy to BT Alex. Brown Incorporated, One Bankers Trust Plaza, 130
Liberty Street, New York, New York 10006, Attention: General Counsel; and if to
the Company, to Aspect Medical Systems, Inc., Two Vision Drive, Natick,
Massachusetts 01760, Attention: Nassib G. Chamoun; with a copy to Hale and Dorr
LLP, 60 State Street, Boston, MA 02109, Attention: Susan Murley, Esq.

     11.  TERMINATION.

          This Agreement may be terminated by you as follows:

<PAGE>   26

                                      -26-


          (a) by notice to the Company at any time prior to the Closing Date if
any of the following has occurred: (i) since the respective dates as of which
information is given in the Registration Statement and the Prospectus, any
material adverse change or any development involving a prospective material
adverse change in or affecting the condition, financial or otherwise, of the
Company or the earnings, business, management, properties, assets, rights,
operations, condition (financial or otherwise) or business prospects of the
Company, whether or not arising in the ordinary course of business, (ii) any
outbreak or escalation of hostilities or declaration of war or national
emergency or other national or international calamity or crisis or change in
economic or political conditions if the effect of such outbreak, escalation,
declaration, emergency, calamity, crisis or change on the financial markets of
the United States would, in your reasonable judgment, make it impracticable or
inadvisable to market the Shares or to enforce contracts for the sale of the
Shares, or (iii) suspension of trading in securities generally on the New York
Stock Exchange or the American Stock Exchange or limitation on prices (other
than limitations on hours or numbers of days of trading) for securities on
either such Exchange, (iv) the enactment, publication, decree or other
promulgation of any statute, regulation, rule or order of any court or other
governmental authority which in your opinion materially and adversely affects or
may materially and adversely affect the business or operations of the Company,
(v) declaration of a banking moratorium by United States or New York State
authorities, (vi) any downgrading, or placement on any watch list for possible
downgrading, in the rating of the Company's debt securities by any "nationally
recognized statistical rating organization" (as defined for purposes of
Rule 436(g) under the Exchange Act); (vii) the suspension of trading of the
Company's common stock by the Nasdaq National Market, the Commission, or any
other governmental authority or, (vii) the taking of any action by any
governmental body or agency in respect of its monetary or fiscal affairs which
in your reasonable opinion has a material adverse effect on the securities
markets in the United States; or

          (b) as provided in Sections 6 and 9 of this Agreement.

     12.  SUCCESSORS.

          This Agreement has been and is made solely for the benefit of the
Underwriters and the Company and their respective successors, executors,
administrators, heirs and assigns, and the officers, directors and controlling
persons referred to herein, and no other person will have any right or
obligation hereunder. No purchaser of any of the Shares from any Underwriter
shall be deemed a successor or assign merely because of such purchase.

     13.  INFORMATION PROVIDED BY UNDERWRITERS.

          The Company and the Underwriters acknowledge and agree that the only
information furnished or to be furnished by any Underwriter to the Company for
inclusion in any Prospectus or the Registration Statement consists of the
information set forth in the last paragraph on the front cover page of the
Prospectus (insofar as such information relates to the Underwriters), the legend
required by Item 502(d) of 

<PAGE>   27

                                      -27-


Regulation S-K under the Act and the information under the caption
"Underwriting" in the Prospectus.

     14.  MISCELLANEOUS.

          The reimbursement, indemnification and contribution agreements
contained in this Agreement and the representations, warranties and covenants in
this Agreement shall remain in full force and effect regardless of (a) any
termination of this Agreement, (b) any investigation made by or on behalf of any
Underwriter or controlling person thereof, or by or on behalf of the Company or
its directors or officers and (c) delivery of and payment for the Shares under
this Agreement.

          This Agreement may be executed in two or more counterparts, each of
which shall be deemed an original, but all of which together shall constitute
one and the same instrument.

          This Agreement shall be governed by, and construed in accordance with,
the laws of the State of Maryland.


<PAGE>   28

                                      -28-



          If the foregoing letter is in accordance with your understanding of
our agreement, please sign and return to us the enclosed duplicates hereof,
whereupon it will become a binding agreement among the Company and the several
Underwriters in accordance with its terms.


                                       Very truly yours,

                                       ASPECT MEDICAL SYSTEMS, INC.


                                       By: _____________________________________
                                           Nassib G. Chamoun
                                           Chief Executive Officer and President



The foregoing Underwriting Agreement 
is hereby confirmed and accepted as
of the date first above written.


BT ALEX. BROWN INCORPORATED
MERRILL LYNCH, PIERCE, FENNER & SMITH INCORPORATED
PIPER JAFFRAY INC.


As Representatives of the several
Underwriters listed on Schedule I


By:  BT Alex. Brown Incorporated



By: _______________________________
    Authorized Representative



<PAGE>   29

                                      -29-



                                   SCHEDULE I


                            SCHEDULE OF UNDERWRITERS

<TABLE>
<CAPTION>
                                                    Number of Firm Shares
        Underwriter                                   to be Purchased
        -----------                                   ---------------

<S>                                                        <C>
BT Alex. Brown Incorporated                                 -
Merrill Lynch & Co.                                         -
Piper Jaffray Inc.                                          -


                                                          ------
           Total
                                                          ======
</TABLE>


<PAGE>   1
 
                                                                    EXHIBIT 23.1
 
                   CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS
 
     As independent public accountants, we hereby consent to the use of our
report and to all references to our Firm included in or made a part of this
registration statement.
 
                                          /s/ Arthur Andersen LLP
 
Boston, Massachusetts
   
July 15, 1998
    

<PAGE>   1
 
                                                                    EXHIBIT 23.2
 
                       CONSENT OF INDEPENDENT ACCOUNTANTS
 
   
     We hereby consent to the use in the Prospectus constituting part of this
Registration Statement on Form S-1 of our report dated July 3, 1996, relating to
the financial statements of Aspect Medical Systems, Inc., which appears in such
Prospectus. We also consent to the references to us under the headings "Experts"
and "Selected Financial Information" in such Prospectus. However, it should be
noted that PricewaterhouseCoopers LLP has not prepared or certified such
"Selected Financial Information."
    
 
   
/s/ PricewaterhouseCoopers LLP
    
 
Boston, Massachusetts
   
July 15, 1998
    

<TABLE> <S> <C>

<ARTICLE> 5
<CURRENCY> U.S.DOLLARS
       
<S>                             <C>
<PERIOD-TYPE>                   6-MOS
<FISCAL-YEAR-END>                          DEC-31-1998
<PERIOD-START>                             JAN-01-1998
<PERIOD-END>                               JUL-04-1998
<EXCHANGE-RATE>                                      1
<CASH>                                       3,300,024
<SECURITIES>                                 6,830,863
<RECEIVABLES>                                1,408,313
<ALLOWANCES>                                   102,310
<INVENTORY>                                    951,129
<CURRENT-ASSETS>                            13,287,436
<PP&E>                                       2,610,721
<DEPRECIATION>                                 713,886
<TOTAL-ASSETS>                              16,125,440
<CURRENT-LIABILITIES>                        6,144,371
<BONDS>                                        681,926
                                0
                                 50,299,886
<COMMON>                                        17,530
<OTHER-SE>                                (41,018,273)
<TOTAL-LIABILITY-AND-EQUITY>                16,125,440
<SALES>                                      4,420,165
<TOTAL-REVENUES>                             4,420,165
<CGS>                                        2,662,249
<TOTAL-COSTS>                                2,662,249
<OTHER-EXPENSES>                             8,571,729
<LOSS-PROVISION>                                40,000
<INTEREST-EXPENSE>                              16,112
<INCOME-PRETAX>                            (6,517,068)
<INCOME-TAX>                                         0
<INCOME-CONTINUING>                        (6,517,068)
<DISCONTINUED>                                       0
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                               (6,517,068)
<EPS-PRIMARY>                                   (6.34)
<EPS-DILUTED>                                   (6.34)
        

</TABLE>


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