MEDIAPLEX INC
S-1/A, 1999-11-12
BUSINESS SERVICES, NEC
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<PAGE>


As filed with the Securities and Exchange Commission on November 12, 1999
                                                     Registration No. 333-86459
- -------------------------------------------------------------------------------
- -------------------------------------------------------------------------------

                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C. 20549

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

                             AMENDMENT NO. 4
                                      TO
                                   FORM S-1
                            REGISTRATION STATEMENT
                                     Under
                          The Securities Act of 1933

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

                                MEDIAPLEX, INC.
            (Exact name of Registrant as specified in its charter)

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

<TABLE>
 <S>                              <C>                                <C>
           Delaware                             7372                          94-3295822
(tateSor other jurisdiction of      (Primary Standard Industrial           (I.R.S. Employer
 ncorporationior organization)       Classification Code Number)        Identification Number)
</TABLE>

                       131 Steuart Street, Fourth Floor
                     San Francisco, California 94105-1230
                                (415) 808-1900
  (Address, including zip code, and telephone number, including area code, of
                   Registrant's principal executive offices)

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

                              Gregory R. Raifman
                     Chairman and Chief Executive Officer
                                Mediaplex, Inc.
                       131 Steuart Street, Fourth Floor
                     San Francisco, California 94105-1230
                                (415) 808-1900
(Name, address, including zip code, and telephone number, including area code,
                             of agent for service)

                                  Copies to:
<TABLE>
<S>                                            <C>
            Aaron J. Alter, Esq.                         Laird H. Simons, III, Esq.
          Tamara G. Mattison, Esq.                        Robert A. Freedman, Esq.
             Linda M. Cuny, Esq.                          R. Gregory Roussel, Esq.
           Robert E. Dawson, Esq.                            Fenwick & West LLP
      Wilson Sonsini Goodrich & Rosati                      Two Palo Alto Square
          Professional Corporation                      Palo Alto, California 94306
             650 Page Mill Road                                (650) 494-0600
      Palo Alto, California 94304-1050
               (650) 493-9300
</TABLE>

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

  Approximate date of commencement of proposed sale to the public: As soon as
practicable after the effective date of this Registration Statement.
  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 of
1933, 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 hereafter 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 such
Section 8(a), may determine.

- -------------------------------------------------------------------------------
- -------------------------------------------------------------------------------
<PAGE>

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+The information in the prospectus is not complete and may be changed. We may  +
+not sell these securities until the registration statement filed with the     +
+Securities and Exchange Commission is effective. This prospectus is not an    +
+offer to sell these securities and it is not soliciting an offer to buy these +
+securities in any state where the offer or sale is not permitted.             +
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

PROSPECTUS    Subject to Completion, dated November 12, 1999

                                6,000,000 Shares

                              [LOGO OF MEDIAPLEX]

                                  Common Stock
- --------------------------------------------------------------------------------

  This is our initial public offering of shares of common stock. We are
offering 6,000,000 shares. No public market currently exists for our shares.

  We propose to list the shares on the Nasdaq National Market under the symbol
"MPLX." Anticipated price range of $8.00 to $10.00 per share.

  Investing in the shares involves risks. "Risk Factors" begin on page 7.

<TABLE>
<CAPTION>
                                                                      Per
                                                                     Share Total
                                                                     ----- -----
<S>                                                                  <C>   <C>
Public Offering Price...............................................  $     $
Underwriting Discount...............................................  $     $
Proceeds to Mediaplex...............................................  $     $
</TABLE>

  We have granted the underwriters a 30-day option to purchase up to 900,000
additional shares of common stock on the same terms and conditions as set forth
above solely to cover over-allotments, if any.

  Neither the Securities and Exchange Commission nor any state securities
commission has approved or disapproved of these securities or determined if
this prospectus is accurate or complete. Any representation to the contrary is
a criminal offense.

  Lehman Brothers expects to deliver the shares on or about     , 1999.

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

Lehman Brothers

           SG Cowen

                   U.S. Bancorp Piper Jaffray

                                                        Fidelity Capital Markets
                              a division of National Financial Services
                              Corporation
                                   Facilitating Electronic Distribution

    , 1999
<PAGE>

                       [INSIDE FRONT COVER OF PROSPECTUS]

[GRAPHIC OF MEDIAPLEX LINKING A COMPANY WITH CUSTOMERS]


Caption: Mediaplex connects the enterprise.


Inside Front Cover Gatefold


[GRAPHIC OF WEB SITE SCREEN SHOTS FOR A SAMPLE APPLICATION OF A MEDIAPLEX
ADVERTISING CAMPAIGN]


Heading across gatefold: MOJO Technology. Integrating business data with online
marketing campaigns to deliver the most relevant message to the right target .
 . . all in real time.


Captions:


EXAMPLE:


Mediaplex managing an online marketing campaign for Tickets.com on the
AudioFind.com Web site.


1.An Internet user in Fort Lauderdale on the AudioFind.com Web site accesses a
page on Female Pop Vocalists.


2.The MOJO platform serves a banner ad for Tickets.com with a message
determined by business rules regarding the geographic profile of the user,
their interest in a particular artist or music category, and the current
Tickets.com auction inventory.


3.The Internet user clicks on the banner ad, arrives at the specific
Tickets.com auction Web site to bid on concert tickets.


4.The MOJO platform records impressions, click-throughs and bid activity for
reporting and return on investment analysis.


*****


Using Mediaplex, Tickets.com:


 .Increased the click-through rates on targeted auction banners 440% over the
generic default banners


 .Improved management of auction ticket inventory
<PAGE>

                               TABLE OF CONTENTS
<TABLE>
<CAPTION>
                                                                          Page
                                                                          ----
<S>                                                                       <C>
Prospectus Summary.......................................................   3
Risk Factors.............................................................   7
Use of Proceeds..........................................................  19
Dividend Policy..........................................................  19
Capitalization...........................................................  20
Dilution.................................................................  21
Selected Financial Data..................................................  22
Selected Pro Forma Financial Data........................................  23
Management's Discussion and Analysis of Financial Condition and Results
 of Operations...........................................................  24
</TABLE>
<TABLE>
<CAPTION>
                                                                            Page
                                                                            ----
<S>                                                                         <C>
Business...................................................................  34
Management.................................................................  50
Related Party Transactions.................................................  59
Principal Stockholders.....................................................  62
Description of Capital Stock...............................................  64
Shares Eligible for Future Sale............................................  67
Underwriting...............................................................  69
Legal Matters..............................................................  72
Experts....................................................................  72
Where You Can Find Additional Information..................................  72
Index to Financial Statements.............................................. F-1
</TABLE>

                             ABOUT THIS PROSPECTUS

  You should rely only on the information contained in this prospectus. We have
not authorized anyone to provide you with information different from that
contained in this prospectus. We are offering to sell, and seeking offers to
buy, shares of common stock only in jurisdictions where offers and sales are
permitted. The information contained in this prospectus is accurate only as of
the date of this prospectus, regardless of the time of delivery of this
prospectus or of any sale of common stock.

  This preliminary prospectus is subject to completion prior to this offering.
Among other things, this preliminary prospectus describes our company as we
currently expect it to exist at the time of this offering.

  See the section of this prospectus entitled "Risk Factors" for a discussion
of various factors that you should consider before investing in the common
stock offered by this prospectus.

  Certain statements under the captions "Prospectus Summary," "Risk Factors,"
"Use of Proceeds," "Management's Discussion and Analysis of Financial Condition
and Results of Operations" and "Business" and elsewhere in this prospectus are
forward-looking statements. These forward-looking statements include, but are
not limited to, statements about our plans, objectives, expectations and
intentions and other statements contained in the prospectus that are not
historical facts. When used in this prospectus, the words "expects,"
"anticipates," "intends," "plans," "believes," "seeks" and "estimates" and
similar expressions are generally intended to identify forward-looking
statements. Because these forward-looking statements involve risks and
uncertainties, there are important factors that could cause actual results to
differ materially from those expressed or implied by these forward-looking
statements, including our plans, objectives, expectations and intentions and
other factors discussed under "Risk Factors."

  Mediaplex(TM), MOJO(TM), the Mediaplex logo, Storyboard Messaging(TM),
Multiple Messaging(TM), eBusiness Messaging(TM) and Queued Creative(TM) are our
trademarks. We have applied to register Mediaplex and MOJO, our trademarks. All
trademarks and trade names appearing in this prospectus are the property of
their respective holders.

  Until         , 1999, all dealers selling shares of the common stock, whether
or not participating in this offering, 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.
<PAGE>

                               PROSPECTUS SUMMARY

  You should read the following summary together with the more detailed
information regarding our company and the common stock being sold in this
offering and the financial statements and notes to those statements appearing
elsewhere in this prospectus.

  Except as otherwise indicated, all information in this prospectus assumes
that the underwriters do not exercise the option granted by Mediaplex to
purchase additional shares in this offering, assumes the conversion of all of
our preferred stock into common stock upon the closing of this offering, and
reflects our reincorporation into Delaware to be effected prior to the
effectiveness of this offering. See "Underwriting."

                                   Mediaplex

  We provide technology-based services that enable companies to integrate their
internal business data with their online advertising and direct marketing
activities to deliver customized messages and offers to Web site visitors. Our
services encompass planning, executing, monitoring and analyzing Web-based
advertising and marketing campaigns, and are based upon our proprietary
technology, tradenamed "MOJO." MOJO is an acronym for "mobile Java objects,"
which are discrete pieces of software written in Java code that perform
specialized functions and communicate with each other. The objects are mobile
because they can reside on our servers or our clients' servers, and can be
moved with ease. Our technology allows companies to change the content of
Internet messages and offers in real time, or virtually instantaneously, in
response to changes in their underlying business variables, such as inventory
levels, product pricing and customer data.

  For example, companies try to avoid marketing goods that are out of stock,
and often want to discount items that are overstocked or perishable, such as
hotel rooms or airline seats. In addition, marketers may wish to target a
particular geographic area or group of consumers. Our technology draws upon a
company's up-to-the-minute business data to tailor the message for an adjusted
price, a different product or mix of products, or any other message the company
would like to communicate. We believe the real-time customization of messages
will increase consumer response to online advertisements and marketing, thereby
improving companies' returns on advertising and marketing expenditures.

  The rapid growth in the worldwide online population and spending related to
e-commerce, or commerce conducted over the Internet, has established the
Internet as an important advertising medium. Forrester Research, Inc.
anticipates that U.S. online advertising spending will grow from $2.8 billion
in 1999 to $17.2 billion in 2003. To date, online advertising has not achieved
effective "one-to-one" marketing, which entails delivery of the right message
to the right consumer at the right time. The ability to send a customized
message in real time remains a significant challenge, which if met, would
enable companies to use the Internet as an effective marketing and sales
channel.

  We believe we are the first company to offer a solution for businesses that
integrates their internal business data with online advertising and direct
marketing campaigns to deliver customized messages to consumers in real time.
The benefits of our services include the following:

  . Comprehensive Online Advertising Campaigns. We provide a wide range of
    online campaign services including strategic planning, consumer
    targeting, media buying, ad serving, and results measurement and
    reporting for advertisements that have been designed and created by our
    clients or their advertising agencies.

  . Real-time Tracking and Measuring of Campaign Results. We continually
    monitor a variety of measures, such as click-through and conversion
    rates, and provide Internet access to performance reports 24 hours a day.

  . Message Re-targeting. We use Internet browser-based tracking tools to
    capture and analyze data on consumer behavior and site visitation
    patterns. We use this data to refine future messages to consumers whom we
    have previously identified.

                                       3
<PAGE>


  . Real-time Messaging. We can change the content and site placement of
    online advertisements in real time. This enables a company to tailor a
    message based on predefined business parameters and a consumer's profile
    in order to deliver the right message virtually instantaneously.

  . Integration of Customers' Business Information. Our MOJO technology
    enables us to integrate business information with an online advertising
    campaign to customize and deliver advertisements in real time based on
    consumer profiles and relevant business information such as inventory and
    pricing levels.

                           Concentration of Customers

  Our top ten clients, based on revenues from January 1, 1999 to September 30,
1999, were Ashford.com, DATEK Online, FreeShop.com, MyShopNow.com, OfficeMax,
ShopNow.com, Strong Funds and uBid and the advertising agencies McCann-
Erickson/A&L and Publicis & Hal Riney, who use our services on behalf of their
clients. We depend on a limited number of clients for our revenues. In 1998,
DATEK Online and uBid accounted for approximately 56% and 21% of our revenues,
respectively, and in the first nine months of 1999, DATEK Online, ShopNow.com
and Publicis & Hal Riney accounted for approximately 17%, 11% and 10% of our
revenues, respectively.

               Our Financial Results and Competitive Environment

  We currently generate the substantial majority of our revenues from
advertising campaign management services. To date, we have not generated
significant revenue from our message management services. We have deployed two
campaigns for our message management services utilizing the real-time messaging
and the components of our MOJO technology that enable integration of the
advertisement with a company's internal business information, which we refer to
as business integration components. Although our revenues have increased from
$3.6 million for all of 1998 to $13.9 million for the first nine months of
1999, we have lost approximately $30.4 million since inception. We have not
been profitable in any quarter and expect to continue to incur losses for the
foreseeable future. We currently operate in a highly competitive market with no
significant barriers to entry.

                Control by Our Executive Officers and Directors

  After the consummation of this offering, our executive officers and directors
will, directly or indirectly, control approximately 19,156,518 million shares
of our common stock, representing approximately 54.4% of the total shares that
will be outstanding. As a result, these persons will be able to control the
election of our directors and other matters requiring stockholder approval.

                     Additional Information about Mediaplex

  Our principal executive offices are located at 131 Steuart Street, Fourth
Floor, San Francisco, California 94105-1230 and our telephone number is (415)
808-1900. Our Web site is located at www.mediaplex.com. Information contained
on our Web site does not constitute part of this prospectus.

  We were incorporated in California in September 1996 as Internet Extra
Corporation. On April 1, 1998, we set up a wholly-owned subsidiary, MediaPlex,
Inc., a California corporation, to conduct our current business. We expect to
merge MediaPlex, Inc. with Internet Extra Corporation and reincorporate the
merged entity under the name "Mediaplex, Inc." in Delaware in November 1999.


                                       4
<PAGE>


                                  The Offering

<TABLE>
 <C>                                    <S>
 Common stock offered by Mediaplex..... 6,000,000 shares

 Common stock outstanding after the
  offering............................. 30,717,365 shares

 Use of proceeds....................... We estimate that we will receive net
                                        proceeds from this offering of
                                        $    49.2 million, or $56.7 million if
                                        the underwriters exercise their over-
                                        allotment option in full. We expect to
                                        use the net proceeds for general
                                        corporate purposes, including working
                                        capital and potential acquisitions. See
                                        "Use of Proceeds."

 Nasdaq National Market symbol......... "MPLX"
</TABLE>

  In addition to the 30,717,365 shares of common stock outstanding after this
offering, as of the closing of this offering and based on the number of shares
issued and options and warrants granted as of September 30, 1999, we expect to
have additional shares of common stock available for issuance under the
following plans and arrangements:

  . 12,130,500 shares issuable under our stock option plans, consisting of:

   . 9,287,198 shares underlying options outstanding at a weighted average
     exercise price of $0.82 per share, of which 5,024,303 were exercisable;
     and

   . 2,843,302 shares available for future issuance;

  . 875,000 shares issuable upon the exercise of warrants outstanding at a
    weighted average exercise price of $0.97 per share; and

  . 400,000 shares available for issuance under our 1999 Employee Stock
    Purchase Plan.


                                       5
<PAGE>

                             Summary Financial Data

  The following table is a summary of our statement of operations. See
"Management's Discussion and Analysis of Financial Condition and Results of
Operations." The financial results for the nine months ended September 30, 1998
and 1999 are unaudited.

<TABLE>
<CAPTION>
                          September 10,       Years Ended           Nine Months
                         1996 (inception)    December 31,       Ended September 30,
                         to December 31,  --------------------  ---------------------
                               1996         1997       1998       1998        1999
                         ---------------- ---------  ---------  ---------  ----------
                              (in thousands, except share and per share data)
<S>                      <C>              <C>        <C>        <C>        <C>
Statement of Operations
 Data:
Revenues................        $  --        $  426    $ 3,588    $ 2,951    $ 13,941
Gross profit (loss).....           --           (19)       817        622       2,992
Loss from operations....         (255)       (1,115)    (1,772)      (833)    (12,827)
Net loss................         (255)       (1,117)    (2,019)    (1,117)    (12,640)
Net loss per share--
 basic and diluted......       $(0.07)      $ (0.13)   $ (0.25)   $ (0.13)   $  (2.05)
Weighted average shares
 used to compute net
 loss per share--basic
 and diluted............    3,795,714     8,457,464  8,186,127  8,591,365  13,074,428
Pro forma net loss per
 share--basic and
 diluted (unaudited)....                               $ (0.25)              $  (1.56)
Weighted average shares
 used to compute pro
 forma net loss per
 share--basic and
 diluted (unaudited)....                             8,186,127             17,280,523
</TABLE>

  The following table is a summary of our balance sheet as of September 30,
1999. The as adjusted column reflects the conversion of all outstanding shares
of preferred stock into common stock upon the closing of this offering and our
receipt of the estimated net proceeds from the sale of the 6,000,000 shares of
common stock offered in this offering at an assumed initial public offering
price of $9.00 per share after deducting the estimated underwriting discount
and offering expenses payable by us. See "Use of Proceeds" and
"Capitalization."

<TABLE>
<CAPTION>
                                                      As of September 30, 1999
                                                      --------------------------
                                                        Actual     As Adjusted
                                                      ------------ -------------
                                                           (in thousands)
<S>                                                   <C>          <C>
Balance Sheet Data:
Cash and cash equivalents............................ $     16,520 $     66,053
Working capital......................................       14,743       64,339
Goodwill.............................................        2,508        2,508
Total assets.........................................       27,492       76,662
Long-term debt.......................................          263          263
Total stockholders' equity...........................       19,762       68,932
</TABLE>

                                       6
<PAGE>

                                  RISK FACTORS

  You should carefully consider the risks described below before making a
decision to buy our common stock. If any of the following risks actually
occurs, our business could be harmed. In that case, the trading price of our
common stock could decline, and you might lose all or part of your investment.
You should also refer to the other information set forth in this prospectus,
including our financial statements and the related notes.

Risks Related to Our Company

Our limited operating history makes financial forecasting and evaluation of our
business difficult.

  We were founded in 1996 and only began selling our advertising campaign
management services in April 1998. In addition, we have only recently begun
deploying our MOJO technology in client advertising campaigns. In the quarter
ended June 30, 1999, we employed portions of our MOJO technology in one
campaign, and in the quarter ended September 30, 1999, in that campaign and
eight additional campaigns. Consequently, we have less than one year of
relevant operating history upon which you may evaluate our operations and
financial prospects. Our limited operating history makes it difficult to
forecast our future operating results, and for you to evaluate our future
revenue and income potential, as well as your investment in our common stock.
In particular, our limited operating history makes it difficult to evaluate our
ability to:

  . purchase appropriate media space at reasonable costs;

  . attract new advertisers and maintain current client relationships;

  . achieve effective ad campaign results for our clients;

  . develop new relationships and maintain existing relationships with
    advertising agencies, our marketing alliance partners and other third
    parties;

  . continue to develop and upgrade our MOJO platform and other technology to
    keep pace with the growth of the Internet advertising industry and
    changes in technology; and

  . continue to expand the number of services we offer.

We have a history of losses, expect future losses and may never become
profitable.

  We have not achieved profitability in any period to date and, given the level
of planned operating and capital expenditures, we expect to continue to incur
losses and negative cash flows for the foreseeable future. Our accumulated
deficit as of September 30, 1999 was approximately $30.4 million. For the year
ended December 31, 1998 and the nine months ended September 30, 1999, we
incurred losses of $2.0 million and $12.6 million, respectively. If our
revenues grow more slowly than we anticipate, or if our operating expenses
exceed our expectations and cannot be adjusted accordingly, our business will
be harmed. Furthermore, if we are unable to generate a long-term profit, we
will eventually have to cease operations.

Variations in quarterly operating results, due to factors such as changes in
demand and the mix of services we provide, may cause our stock price to
decline.

  It is possible that in future periods our results of operations will be below
the expectations of securities analysts. If so, the market price of your shares
would likely decline. Our quarterly operating results have fluctuated in the
past and are likely to continue to do so in the future. For example, in the
past two calendar years, our revenues increased substantially in the quarters
ended June 30 from the revenues generated in the immediately preceding
quarters. In addition, revenues declined in the quarter ended December 31,
1998. We believe that quarter-to-quarter comparisons of our operating results
are not a good indication of our future performance and should not be relied
upon to predict our future performance or our stock price.

                                       7
<PAGE>

  Our quarterly revenues, expenses and operating results could vary
significantly from quarter-to-quarter for several other reasons, many of which
are beyond our control. These factors include:

  . demand for our advertising services and mix of services we provide;

  . addition of new or loss of current advertisers and advertising agencies;

  . decisions by advertisers or advertising agencies to implement or delay
    campaigns;

  . deployment of new services we may offer;

  . changes in availability and pricing of advertising space;

  . changes in our pricing policies or the pricing policies of our
    competitors; and

  . costs related to acquisitions of technology or businesses.

  Our current and future expense estimates are based, in large part, on
estimates of future revenues, which are difficult to predict, and on our
investment plans. In particular, we plan to increase our operating expenses
significantly in order to expand our sales and marketing operations, to enhance
our proprietary software and to expand internationally. We may be unable to, or
may elect not to, adjust spending quickly enough to offset any unexpected
revenues shortfall. If these expenses are not accompanied by increased
revenues, our results of operations and financial condition would be harmed.

Our revenues depend upon a few key clients, and if we lose a major client, our
revenues may be significantly reduced.

  Our revenues have been derived from a limited number of advertisers and
advertising agencies that use our services. Our quarterly and annual results of
operations would be harmed by the loss of any of these clients. In 1998, DATEK
Online and uBid accounted for approximately 56% and 21% of our revenues,
respectively. In the first nine months of 1999, DATEK Online, ShopNow.com and
Publicis & Hal Riney accounted for approximately 17%, 11% and 10% of our
revenues, respectively. In addition, four customers accounted for 76% of our
outstanding accounts receivable at December 31, 1998 and three customers
accounted for 50% of our outstanding accounts receivable at September 30, 1999.
We expect that some of these entities may continue to account for a significant
percentage of our revenues for the foreseeable future. Advertisers typically
purchase advertising that runs for a limited time under short-term arrangements
ranging from 30 days to one year. None of our clients is currently purchasing
our advertising services under a long-term contract. Current advertisers may
not continue to purchase advertising from us or we may not be able to
successfully attract additional advertisers. In addition, the non-payment or
late payment of amounts due to us from a significant advertiser or ad agency
could harm our financial condition. Further, our advertising agency customers
may develop online message management capabilities in-house, thus eliminating
their need for our services.

If we fail to establish, maintain and expand our business and marketing
alliances, our ability to grow could be limited, we may not achieve desired
revenues and our stock price may decline.

  In order to grow our business, we must generate, retain and strengthen
successful business and marketing alliances with companies in industries
including:

  . Internet and traditional media advertising;

  . business software;

  . Web site development and consulting; and

  . information technology consultants.

  We depend, and expect to continue to depend, on our business and marketing
alliances, which are companies with which we have written or oral agreements to
work together to provide services to our clients, to refer business from their
clients and customers to us. If companies with which we have business and

                                       8
<PAGE>

marketing alliances do not refer their clients and customers to us to perform
their online campaign and message management, our revenues and results of
operations would be severely harmed. We currently expect that a significant
amount of our future revenues will need to be generated through these
relationships. In addition, if companies with which we have business and
marketing alliances do not provide high quality products and services to our
mutual clients, our sales could suffer. We have little control over the amount
of resources these companies will devote to online advertising or referring
their clients to our services. We may not be able to generate and maintain
adequate relationships to offset the significant resources that are necessary
to develop marketing efforts to reach clients of our business and marketing
alliances.

We are substantially dependent upon our MOJO technology for our future
revenues, and if our MOJO technology does not generate revenues, our business
may fail.

  We believe that our future revenues are substantially dependent on the
acceptance by clients of the use of our MOJO technology, which we believe is
the cornerstone of our business. If our MOJO technology does not perform as
anticipated or otherwise does not attract clients to use our services, our
operations will suffer. We began using our MOJO technology to provide
advertising and direct marketing services in April 1999, and have only used
portions of it in nine campaigns as of September 30, 1999. We have only
recently introduced message management services using our MOJO technology and
these services remain largely untested. In addition, we have incurred and will
continue to incur significant expense developing our MOJO technology. If our
revenues generated from the use of our MOJO technology do not cover these
development costs, our financial condition would suffer.

Our MOJO technology is relatively new and untested; if our MOJO technology does
not perform as anticipated, we would need to devote significant resources to
address defects, and our reputation would be damaged.

  Our MOJO technology is complex and has had, and may have in the future,
errors, defects or performance problems. In particular, we may encounter
problems when it is more broadly used or when it is updated to expand and
enhance its capabilities. Although we have internally tested our MOJO
technology extensively, we have only used portions of it in nine campaigns as
of September 30, 1999. Consequently, our technology may still malfunction or
suffer from design defects. If our technology malfunctions or contains such
defects, our services may not be reliable or compatible in certain online
environments used by our clients. In such instances, we would need to devote
significant resources to address these defects, and any problems could result
in lost revenues and damage to our reputation.

If our MOJO technology suffers from design defects, we may need to expend
significant resources to address resulting product liability claims.

  Our business will be harmed if our MOJO technology suffers from design
defects and, as a result, we become subject to significant product liability
claims. Technology as complex as ours may contain design defects which are not
detectable even after extensive internal testing. Such defects may become
apparent only after widespread commercial use. Our contracts with our clients
currently do not contain provisions to limit our exposure to liabilities
resulting from product liability claims. We currently do not carry any
insurance against product liabilities. Although we have not experienced any
product liability claims to date, we cannot assure you that we will not do so
in the future. Any product liability claim brought against us could materially
harm our business.

If we fail to effectively manage our growth, our management and resources could
be strained and our ability to capture new business could suffer.

  We have grown significantly since our inception and expect to grow quickly in
the future. Future expansion could be expensive and strain our management and
other resources.

                                       9
<PAGE>

  As we continue to increase the scope of our operations, we will need an
effective planning and management process to implement our business plan
successfully in the rapidly evolving market for Internet advertising. Our
failure to manage this growth could seriously harm our business. We have
increased our number of employees from 7 at September 30, 1998 to 109 at
September 30, 1999. In addition, we have recently opened a sales office in
Germany and we anticipate that we will further expand international operations
in 2000.

The loss of our key personnel, including our chief executive officer, president
and chief operating officer, or any inability to attract and retain additional
personnel, could affect our ability to grow our business.

  Our future success depends to a significant extent on the continued service
of our key senior management, technical and professional service and support
personnel. The loss of the services of any member of our management team, in
particular our chief executive officer, president and chief operating officer,
would harm our business. We have employment agreements with only some of our
key senior management, namely, Gregory R. Raifman, Jon L. Edwards, Barclay
Jiang and Walter Haefeker. All of our other employees are at-will. Because of
the substantial competition for qualified personnel in Northern California, we
could suffer substantial attrition and could lose key members of our
management. We would also be harmed if one or more of our officers or key
employees decided to join a competitor or otherwise compete with us. In
addition, because many of our executives, including our chief financial
officer, have only recently joined us, our management team has only worked
together for a short time and may not work effectively together.

  Our future success also depends on our continuing ability to attract, retain
and motivate highly skilled employees. Competition for qualified personnel in
the high technology industry is intense, particularly in the San Francisco Bay
region of Northern California, where our principal offices are located. If we
fail to hire and retain a sufficient number of sales, marketing, technical,
service and support personnel, we will not be able to maintain or expand our
business.

Our sales and implementation cycle is lengthy, which could divert our financial
and other resources, and is subject to delays, which could result in delayed
revenues.

  If the sales and implementation cycle of our services is delayed, our
revenues will likewise be delayed. Our sales and implementation cycle is
lengthy, causing us to recognize revenues long after our initial contact with a
client. During our sales effort, we spend significant time educating
prospective clients on the use and benefit of our campaign and message
management services. As a result, the sales cycle for our products and services
is long, ranging from a few weeks to several months for our larger clients. The
sales cycle for our new message management services is likely to be longer than
the sales cycle for our other current campaign management services because we
believe that clients may require more extensive approval processes related to
integrating internal business information with their online advertising
campaigns. In addition, in order for a client to implement our services, the
client must commit a significant amount of resources over an extended period of
time. Furthermore, even after a client purchases our services, the
implementation cycle is subject to delays. These delays may be caused by
factors within our control, such as possible technology defects, as well as
those outside our control, such as clients' budgetary constraints, internal
acceptance reviews and the complexity of clients' online advertising needs.

If we are unable to develop relationships with suppliers of profiling services
or obtain or develop profiling technology, we may not be able to attract new
clients or retain our existing clients, which could limit our growth.

  In order for our services to be effective, we rely on the technology of
third-party vendors that implement technologies, called profiling technologies,
which can identify the particular audience to be targeted with an advertising
message. If we are unable to develop relationships with suppliers of profiling
services or obtain or develop profiling technology, our clients will not be
able to realize the full potential that our services and technology offer. As a
result, our ability to attract new clients will be hampered and we may lose
clients. We cannot assure you that we can obtain or develop profiling
technology in a cost-effective and timely manner, if at all.

                                       10
<PAGE>

Sustained or repeated system failures could significantly disrupt our
operations, cause client dissatisfaction and reduce our revenues.

  The continuing and uninterrupted performance of our computer systems is
critical to our success. Our operations depend on our ability to protect our
computer systems against damage from fire, power loss, water damage,
telecommunications failures, viruses, vandalism and other malicious acts, and
similar unexpected adverse events, including earthquakes. Although we maintain
system backup and auxiliary systems to mitigate the damage from the occurrence
of any of these events, we may not have taken adequate steps to guard against
every difficulty that could occur. Clients may become dissatisfied by any
system failure that interrupts our ability to provide our services to them,
including failures affecting the ability to deliver advertisements quickly and
accurately to the targeted audiences. Sustained or repeated system failures
would reduce significantly the attractiveness of our solutions to advertisers.

  In addition, interruptions in our services could result from the failure of
our telecommunications providers to provide the necessary data communications
capacity in the time frame required. Our ad network operations and computer
hardware is primarily housed at Verio, Inc. and AboveNet Communications, Inc.,
third-party providers of Internet communication services located in San
Francisco and San Jose, California, respectively. In addition, the failure of
any advertising server system such as ours or DoubleClick's, including failures
that delay the delivery of advertisements to Internet sites, could reduce
client satisfaction and severely harm our business, results of operations and
financial condition.

  In the past, users have occasionally experienced difficulties due to software
incompatibility or system failures unrelated to our systems. In particular, on
two occasions our network operations and computer hardware located in San
Francisco experienced power failures that affected our ability to deliver our
ad serving services for fifteen minutes and one hour, respectively. On another
occasion, the same facility had network routing problems that caused a high
number of retries to serve ads, which slowed down our ad serving operations.
Although these disruptions have not had a material effect on our business, any
further disruption in the Internet access provided by third-party providers or
any failure of third-party providers to handle higher volumes of user traffic
could seriously harm our business, results of operations and financial
condition.

Our technology has not yet been fully tested at higher capacities, and capacity
constraints could reduce our advertising revenues.

  The volume of advertising delivered through our servers has increased from 1
million impressions per day in January 1999 to up to 36 million impressions per
day as of September 30, 1999, representing approximately one-third of our
capacity at that date. Although to date we have not had difficulties in meeting
demand for our services, further increases in the volume of advertising
delivered through our servers could strain the capacity of our MOJO technology
platform, which could lead to slower response times or system failures. This
would adversely affect the availability of advertisements, the number of
impressions received by advertisers and our advertising revenues. If we do not
effectively address capacity constraints or system failures, our business,
results of operations and financial condition would be harmed.

Acquisitions or strategic investments may divert our management's attention and
consume resources necessary to sustain our business.

  In March 1999, we acquired Netranscend Software, Inc., a Java-based business
automation solutions software company. We intend to continue pursuing selective
acquisitions of businesses and technologies to complement our current business.
Any future acquisition or investment may result in the use of significant
amounts of cash, potentially dilutive issuances of equity securities, the
incurrence of debt, and amortization expenses related to goodwill and other
intangible assets. In addition, acquisitions involve numerous risks, any of
which could harm our business, operating results or financial condition
including:

  . difficulties in the integration and assimilation of the operations,
    technologies, services and personnel of an acquired business;

                                       11
<PAGE>

  . diversion of management's attention from other business concerns;

  . unavailability of favorable financing for future acquisitions; and

  . potential loss of key employees in any acquired business.

The patent application related to our MOJO technology is pending; if a patent
does not issue, we may not be able to prevent competitors from using our
technology.

  In July 1999, we filed a patent application related to our key proprietary
technology platform, MOJO, with the U.S. Patent and Trademark Office. Our
application is currently being reviewed by the U.S. Patent and Trademark
Office, and we have no assurance that a patent will issue. If no patent issues,
we will rely primarily on trade secret law to protect our MOJO technology,
which may be more difficult to monitor and enforce. Even if we are issued a
patent, third parties could successfully design around the patent to offer a
competing service, and we could still be subject to claims of infringement from
third parties.

If we fail to develop new technology-based services or improve our existing
technology-based services to adapt to the changing needs and standards of the
Internet advertising industry, sales of our services will decline.

  The Internet advertising markets are characterized by rapidly changing
technologies, evolving industry standards, frequent new product and service
introductions and changing client demands. The introduction of new services
embodying new technologies and the emergence of new industry standards and
practices could render our existing services obsolete and unmarketable or
require unanticipated investments in research and development. Our failure to
adapt successfully to these changes could harm our business, results of
operations and financial condition.

  Our future success will depend on our ability to adapt to rapidly changing
technologies, to enhance existing technologies and to partner or develop and
introduce a variety of new technology-based services to address our clients'
changing demands. For example, advertisers may require the ability to deliver
advertisements utilizing new rich media formats and more precise consumer
targeting techniques. In addition, increased availability of broadband Internet
access is expected to enable the development of new services that take
advantage of this expansion in delivery capability. We may also experience
difficulties that could delay or prevent the successful design, development,
introduction or marketing of our technology-based services. In addition, any
new technologies or enhancements that we develop must meet the requirements of
our current and prospective clients and must achieve significant market
acceptance. Material delays in introducing new technology-based services and
enhancements may cause clients to forego purchases of our services and purchase
those of our competitors.

  A key component of our strategy is to enhance the return on investment and
other performance measurements for our advertiser and advertising agency
clients. We have limited experience in implementing and following such a
strategy and this strategy may not succeed.

We intend to expand our international sales efforts but do not have substantial
experience in international markets.

  We opened a sales office in Germany in August 1999 and expect to initiate
operations in selected additional international markets in 2000. As of
September 30, 1999, we had not generated any revenues from international
operations. We have limited experience in marketing, selling and supporting our
services abroad, and we consequently may not be successful in these
international markets. Expansion into international markets will require
extensive management attention and resources.

  We also may enter into a number of international alliances as part of our
international strategy and rely on these prospective business alliances to
conduct operations, establish local networks, aggregate Internet sites and
coordinate sales and marketing efforts. Our success in international markets
will depend on the success of our

                                       12
<PAGE>

business alliances and their willingness to dedicate sufficient resources to
our relationships. In the future, any international operations we commence will
be subject to other risks, including:

  . difficulties and costs of staffing and managing foreign operations;

  . seasonal reductions in business activity;

  . the impact of recessions in economies outside the United States;

  . changes in regulatory requirements;

  . export restrictions, including export controls relating to encryption
    technology;

  . reduced protection for intellectual property rights in some countries;

  . potentially adverse tax consequences;

  . political and economic instability;

  . tariffs and other trade barriers; and

  . fluctuations in currency exchange rates.

  Our failure to address these risks adequately may severely harm our ability
to expand our operations internationally.

If others claim that we are infringing their intellectual property, we could
incur significant expenses or be prevented from selling our services.

  Third parties may claim that we are infringing their intellectual property
rights. In particular, third parties may claim that our MOJO technology, on
which our success depends in large part, infringes their intellectual property
rights. While we do not believe that our technology infringes the proprietary
rights of third parties, we may be unaware of intellectual property rights of
others that may cover some of our technology. If any claims of infringement are
brought against us, we could incur significant expenses defending against those
claims, and suffer additional damages if our defense is not successful.

  Any litigation regarding our intellectual property could be costly and time-
consuming and divert the attention of our management and key personnel from our
business operations. The complexity of the technology involved and the
uncertainty of intellectual property litigation increase these risks. Claims of
intellectual property infringement might also require us to enter into royalty
or license agreements; however, we may not be able to obtain royalty or license
agreements on terms acceptable to us, or at all. We also may be subject to
significant damages or an injunction against the use of our services. A
successful claim of patent or other intellectual property infringement against
us would immediately harm our business and financial condition.

We may not be able to protect our technology from unauthorized use, which could
diminish the value of our services, weaken our competitive position and reduce
our revenues.

  Our success depends in large part on our proprietary technology, including
our MOJO platform. In addition, we believe that our Mediaplex and MOJO
trademarks are key to identifying and differentiating our services from those
of our competitors. We may be required to spend significant resources to
monitor and police our intellectual property rights. If we fail to successfully
enforce our intellectual property rights, the value of our services could be
diminished and our competitive position may suffer.

  We rely on a combination of patent, copyright, trademark and trade secret
laws, confidentiality procedures and licensing arrangements to establish and
protect our proprietary rights. Third-party software providers could copy or
otherwise obtain and use our technology without authorization or develop
similar technology independently which may infringe our proprietary rights. We
may not be able to detect infringement and may lose competitive position in the
market before we do so. In addition, competitors may design around our
technology or develop competing technologies. Intellectual property protection
may also be unavailable or limited in some foreign countries.

                                       13
<PAGE>

  We generally enter into confidentiality or license agreements with our
employees, consultants, vendors, clients and corporate partners, and generally
control access to and distribution of our technologies, documentation and other
proprietary information. Despite these efforts, unauthorized parties may
attempt to disclose, obtain or use our services or technologies. Our
precautions may not prevent misappropriation of our services or technologies,
particularly in foreign countries where laws or law enforcement practices may
not protect our proprietary rights as fully as in the United States.

Potential year 2000 problems with our internal systems or third-party systems
could disrupt operations and harm our business.

  We depend on the uninterrupted availability of the Internet infrastructure to
conduct our business. We rely on the continued operations of the computer
systems of our vendors, in particular, those vendors whose Web sites host our
clients' advertisements, and the computer systems of our clients. A failure of
these systems to correctly recognize dates beyond December 31, 1999 could
disrupt operations and harm our business. The successful implementation of our
media messaging services for our clients requires our technology to interact
with our clients' internal business computer systems. If our clients' computer
systems fail because the systems are not year 2000 compliant, we will be unable
to fully deliver the services that our clients may have requested, and our
revenues would decrease. In addition, the failure of a client to receive the
performance reports of the advertisements served due to a failure of its
computer systems would hamper the effectiveness of our services for that
client. Interruptions in the Internet infrastructure affecting us, our clients
or our vendors, or failure of the year 2000 compliance efforts of one or more
of our clients or vendors, could harm our ability to generate revenue and, if
severe, our business, results of operations and financial condition. In the
worst case, any failure in the Internet infrastructure could prevent us from
serving advertisements for our clients for a period of time, resulting in lower
revenues and client complaints. We currently do not have any special
contingency plans for a failure of the Internet infrastructure due to year 2000
issues. A lengthy Internet infrastructure failure could materially harm our
business, financial condition and results of operations.

  Many currently installed computer systems and software products worldwide are
coded to accept only two-digit entries to identify a year in the date code
field. Consequently, on January 1, 2000, many of these systems could fail or
malfunction because they are not able to distinguish between the year 1900 and
the year 2000. Accordingly, many companies, including ourselves and our
clients, potential clients, vendors and business and marketing alliances, may
need to continue to upgrade their systems to comply with applicable year 2000
requirements.

  Additionally, our failure to provide year 2000 compliant services to our
clients could result in financial loss, reputational harm and legal liability
to us. See "Management's Discussion and Analysis of Financial Condition and
Results of Operations--Year 2000 Compliance."

Risks Related to Our Industry

Future restrictions or regulations related to privacy concerns and inadequate
security on the Internet could limit the effectiveness of and reduce the demand
for our services and technology.

  The effectiveness of our services and technology relies on the effectiveness
of techniques for profiling Internet users, which may raise privacy concerns.
Our clients generally have implemented security features to protect the privacy
and integrity of the data collected from their users. However, this information
may be susceptible to hacker interception, break-ins and disruption. If any of
these were to occur, or if a well-publicized compromise of security were to
occur, Internet usage may not increase at the rate we expect and, consequently,
our services would be perceived as less effective or desirable by our clients.

  Visitors to Web sites on which our advertising messages are placed may not be
aware that information regarding them is being collected by third-party data
profiling companies. There currently exists software that can limit the
effectiveness of data profiling technology in capturing information for a
particular visitor to a Web

                                       14
<PAGE>

site. Widespread use of this limiting or inhibiting technology would decrease
the effectiveness of our services for our clients that are dependent upon the
reliability of the information we obtain from profiling companies, which would
decrease the attractiveness of those services to our clients. If this occurs,
our business would be significantly harmed.

  In addition, due to privacy concerns, some Internet commentators, advocates
and governmental bodies have suggested that the use of some of these techniques
for profiling users be limited or eliminated altogether. It is possible in the
future that federal, state or other governmental entities may restrict the
gathering and use of such profile information. If the gathering of profiling
information were to be curtailed in any way, our services would be less
effective, which would harm our business.

  The European Union has recently adopted a directive addressing data privacy
that may result in limitations on the collection and use of certain information
regarding Internet users. These limitations may limit our ability to target
advertising or collect and use information in most European countries. Since
most EU member states have not implemented regulations with respect to the
directive at this time, we cannot yet determine the impact of the directive on
us. However, we are aware that Germany, in particular, has adopted significant
restrictions on the use of some kinds of profiling techniques, including
techniques that third-party profiling companies, on which we rely for data,
often use. Widespread adoption of these kinds of restrictions in other
countries could decrease our ability to provide our advertising and direct
marketing services effectively in those countries, which would hamper our
ability to expand our operations internationally.

Our business model and ability to generate significant revenues depend upon
broad market acceptance of Internet advertising.

  Our business model relies on revenues generated primarily by providing
Internet advertising services to response-oriented advertisers. The Internet as
an advertising medium has not been in existence for a sufficient period of time
to demonstrate its effectiveness. Internet advertising, as well as technology-
based methods for targeting advertising and tracking, measuring and reporting
the results of Internet advertising may not achieve broad market acceptance.
Our ability to generate significant revenues from advertisers will depend, in
part, on our ability to:

  . demonstrate to advertisers that advertising on the Internet will add
    value and increase marketing effectiveness;

  . attract and retain advertisers and advertising agencies by
    differentiating the services and technology we offer; and

  . obtain adequate available advertising inventory from a large base of
    Internet sites.

  There are filter software programs available that limit or prevent
advertising from being delivered to a user's computer. The commercial viability
of Internet advertising would be limited by widespread adoption of these
programs.

Intense competition in the Internet advertising industry could reduce our
ability to gain clients and might require us to reduce prices, which could
reduce our revenues.

  We face intense competition in the Internet advertising services industry.
The following categories represent current and potential competition:

  . providers of online media planning and buying services, such as Avenue A;

  . ad serving companies, such as AdForce, DoubleClick and Engage
    Technologies;

  . publisher networks that provide services directly to clients, such as
    Flycast Communications and 24/7 Media;

                                       15
<PAGE>

  . organizations that manage affiliate programs, such as LinkShare; and

  . advertising agencies that have or elect to develop in-house online media
    management capabilities, such as Lowe Interactive.

  We believe that our ability to compete depends upon many factors both within
and outside of our control, including:

  . the effectiveness, ease of use, performance and features of our
    technology;

  . client perceptions of the effectiveness of our services and technology;

  . the price of our services;

  . our ability to service our clients effectively over a broad geographic
    basis; and

  . the timing and acceptance of new services and enhancements to existing
    solutions developed by us or our competitors.

  The intense competition among Internet sites has led to the creation of a
number of pricing alternatives for Internet advertising. These alternatives
make it difficult for us to project future levels of advertising revenues and
applicable gross margins that can be sustained either by us or the Internet
advertising industry in general.

  We expect competition to continue to increase in our industry because there
are no substantial barriers to entry. In particular, advertising agencies
without in-house online media management capabilities, including those with
which we currently work, may develop these capabilities in the future. We
believe that, in addition, competition will continue to increase as a result of
industry mergers, partnerships and consolidations. For example, AdForce and
Flycast have recently been acquired by CMGI, AdKnowledge has recently been
acquired by Engage Technologies, a subsidiary of CMGI, and NetGravity has
recently been acquired by DoubleClick. As we expand internationally, we expect
to face competition from internationally-based competitors such as Mindshare
Digital and Publicis Technology, as well as our domestic competitors with
international operations, such as BBDO Interactive, Leo Burnett and the
Interpublic Group. Companies doing business on the Internet, including ours,
must also compete with television, radio, cable and print media for a share of
advertisers' total advertising budgets. Advertisers may be reluctant to devote
a significant portion of their advertising budget to Internet advertising if
they perceive the Internet to be a limited or ineffective advertising medium.
In addition, as we expand the scope of our Internet advertising and direct
marketing services, we may compete with a greater number of Internet sites and
other media companies across a wide range of different Internet services.
Competitive pressures could prevent us from growing, reduce our market share or
require us to reduce prices on our services, any of which could harm our
business.

  Many of our existing competitors have significantly greater financial,
technical, marketing, service and other resources, have a larger installed base
of users, have been in business longer or have greater name recognition than we
do. Some of our competitors' services may be more effective than our services
at performing particular functions or be more customized for particular needs.
Some large companies may attempt to build functions into their services that
are similar to functions of our services. Even if these functions are more
limited than those provided by our services, those services could discourage
potential clients from purchasing our services, as well as lead to price
reductions that could harm our revenues. In addition, companies larger than
ourselves may be more successful in purchasing advertising space.

Seasonality and cyclical spending may cause fluctuations in our quarterly
revenue, which may cause us to miss our revenue projections and result in a
decline in our stock price.

  We believe that our revenues will be subject to seasonal fluctuations because
advertisers generally place fewer advertisements during the first and third
calendar quarters of each year. In addition, expenditures by advertisers tend
to be cyclical, reflecting overall economic conditions as well as budgeting and
buying patterns. A decline in the economic prospects of advertisers or the
economy generally could cause companies to

                                       16
<PAGE>

discontinue, delay or reduce online advertising spending. These events could
reduce the demand for our services and cause a decline in our stock price.

Potential clients in specific industries may require us to refuse business from
their competitors, limiting our business opportunities and stunting our revenue
growth.

  To use our services most effectively, advertisers must integrate their
internal business data into their advertising campaigns to deliver a targeted
message. This type of integration may raise privacy concerns and prompt our
clients to require us to contract with them exclusively within their specific
industry. If our clients impose these restrictions on us, our potential client
base and revenue growth would be limited.

  To fully utilize our MOJO-based services, we must have access to our clients'
proprietary business data. Many companies are wary of third parties having
access to their business information, because access by third parties increases
the risk that confidential business data may become known, even if
unintentionally, to outsiders who are not the intended recipients of the data.
These privacy concerns may be so great as to prompt our clients to attempt to
contractually prohibit us from managing the online advertising campaigns of
their competitors. If our potential client base in a particular industry was
limited in this way, our business and future revenues could be harmed. To date,
a few clients have requested that we do not service their competitors; however,
we have not agreed to these requests. To address our clients' concerns, we have
established procedures to ensure the protection of our clients' data, such as
the use of separate teams to work with each client and the use of separate,
secure servers for clients' advertising and message campaigns where a conflict
may exist. However, we cannot assure you that these measures will be adequate
for our clients to continue to use our services.

Government regulation and legal uncertainties of doing business on the Internet
may inhibit the commercial acceptance of the Internet and result in decreased
demand for our services.

  Laws and regulations that apply to Internet communications, commerce and
advertising are becoming more prevalent. These regulations could affect the
costs of communicating on the Internet and adversely affect the growth in use
of the Internet. In turn, these regulations could result in decreased demand
for our services or otherwise harm our business.

  Recently, the United States Congress enacted Internet legislation regarding
children's privacy, copyrights and taxation. A number of other laws and
regulations may be adopted covering issues such as user privacy, pricing,
acceptable content, taxation and quality of products and services. This
legislation could hinder growth in the use of the Internet generally and
decrease the acceptance of the Internet as a communications, commercial and
advertising medium. In addition, the growing use of the Internet has burdened
existing telecommunications infrastructure and has caused interruptions in
telephone service. Certain telephone carriers have petitioned the government to
regulate and impose fees on Internet service providers and online service
providers in a manner similar to long distance carriers.

  Due to the global nature of the Internet, it is possible that, while our
transmissions originate in California, the governments of other states or
foreign countries might attempt to regulate our transmissions or levy sales or
other taxes relating to our activities. The laws governing the Internet remain
largely unsettled, even in areas where there has been some legislative action.
It may take years to determine whether and how existing laws including those
governing intellectual property, privacy, libel and taxation apply to the
Internet and Internet advertising. In addition, the growth and development of
the market for Internet commerce may prompt calls for more stringent consumer
protection laws, both in the United States and abroad, that may impose
additional burdens on companies conducting business over the Internet. Our
business could be adversely affected by the adoption or modification of laws or
regulations relating to the Internet.

Spending by our clients to evaluate and address year 2000 compliance could
result in lower demand for our services.

  In 1999, a significant number of companies, including some of our current
clients, may be required to devote a substantial amount of their information
technology resources to test systems for year 2000 compliance

                                       17
<PAGE>

and fix existing year 2000 problems. If these clients also defer purchases of
our services until year 2000 problems have been resolved, it will depress our
sales in the near term.

Risks That May Cause Your Investment in Our Stock to Decline

Because our directors and executive officers together own a large percentage of
our voting stock, your voting power may be limited, which may prevent an
acquisition of our company or depress our stock price.

  After this offering, it is anticipated that our executive officers and
directors will beneficially own or control, directly or indirectly, 18,914,738
million shares of common stock, which in the aggregate will represent
approximately 53.7% of the outstanding shares of common stock. As a result, if
these persons act together, they will have the ability to control all matters
submitted to our stockholders for approval, including the election and removal
of directors and the approval of any business combination. This may delay or
prevent an acquisition or affect the market price of our stock.

As a new investor, you will experience immediate and substantial dilution of
your investment.

  If you purchase shares of our common stock in this offering, you will
experience immediate and substantial dilution in pro forma net tangible book
value of $6.84 per share. If the holders of outstanding options and warrants
exercise those options, you will experience further dilution.

An active public market for our common stock may not develop, which could
impede your ability to sell your shares and depress our stock price.

  Before this offering, you could not buy or sell our common stock on a public
market. An active public market for our common stock may not develop or be
sustained after the offering, which could affect your ability to sell your
shares and depress the market price of your shares. The market price of your
shares may fall below the initial public offering price.

Future sales of our common stock, including those purchased in this offering,
may depress our stock price.

  Sales of a substantial number of shares of our common stock in the public
market by our stockholders after this offering could depress the market price
of our common stock and could impair our ability to raise capital through the
sale of additional equity securities. Based on shares outstanding as of
September 30, 1999, upon completion of this offering we will have outstanding
30,717,365 shares of common stock, assuming no exercise of the underwriters'
overallotment option. Of these shares, the 6,000,000 shares of common stock
sold in this offering and an additional 55,000 shares of common stock will be
freely tradable, without restriction, in the public market. An additional
75,814 shares of common stock will become freely tradeable 90 days from the
date of this prospectus. After the lockup agreements pertaining to this
offering expire 180 days from the date of this prospectus, an additional
15,826,551 shares will be eligible for sale in the public market.

  In addition, 4,950,429 of the shares subject to outstanding options and
warrants will be exercisable, and if exercised, available for sale 180 days
after the date of this prospectus. See "Shares Eligible for Future Sale" for a
description of shares of common stock that are available for future sale.

We have adopted anti-takeover provisions in our charter documents that could
delay or prevent an acquisition of our company.

  Our certificate of incorporation and bylaws contain provisions, such as
undesignated preferred stock, a staggered board and the restriction on the
persons that can call special board or stockholder meetings, which could make
it more difficult for a third-party to acquire us without the consent of our
board of directors. While we believe these provisions provide for an
opportunity to receive a higher bid by requiring potential acquirors to
negotiate with our board of directors, these provisions may apply even if the
offer may be considered beneficial by some stockholders.

                                       18
<PAGE>

                                USE OF PROCEEDS

  Our net proceeds from the sale of the 6,000,000 shares of common stock
offered in this offering at an assumed initial public offering price of $9.00
per share, after deducting the estimated underwriting discount and offering
expenses payable by us will be approximately $49.2 million. If the
underwriters' over-allotment option is exercised in full, our net proceeds will
be approximately $56.7 million.

  We expect to use approximately $7.5 million of the net proceeds for capital
expenditures and the majority of the net proceeds for working capital and other
general corporate purposes. In addition, we may use a portion of the net
proceeds to acquire complementary products, technologies or businesses;
however, we currently have no commitments or agreements and are not involved in
any negotiations to do so.

  Pending use of the net proceeds of this offering, we intend to invest the net
proceeds in short-term, interest-bearing, investment-grade marketable
securities.

                                DIVIDEND POLICY

  We have never declared or paid any dividends on our capital stock. We
currently expect to retain future earnings, if any, for use in the operation
and expansion of our business and do not anticipate paying any cash dividends
in the foreseeable future.

                                       19
<PAGE>

                                 CAPITALIZATION

The following table sets forth our capitalization as of September 30, 1999. Our
capitalization is presented:

  . on an actual basis;

  . on a pro forma basis to give effect to the automatic conversion of all
    outstanding shares of convertible preferred stock into shares of common
    stock effective upon the closing of this offering; and

  . on a pro forma as adjusted basis to reflect our receipt of the estimated
    net proceeds from the sale of the 6,000,000 shares of common stock
    offered in this offering at an assumed initial public offering price of
    $9.00 per share and after deducting the estimated underwriting discount
    and offering expenses payable by us.

<TABLE>
<CAPTION>
                                                      September 30, 1999
                                                --------------------------------
                                                                      Pro Forma
                                                 Actual   Pro Forma  As Adjusted
                                                --------  ---------  -----------
                                                        (in thousands)
<S>                                             <C>       <C>        <C>
Long-term debt................................. $    263  $    263    $    263
                                                --------  --------    --------
Stockholders' equity:
Convertible preferred stock, $.0001 par value,
 9,981,000 shares authorized, 9,706,000 issued
 and outstanding, actual; 10,000,000 shares
 authorized, no shares issued or outstanding,
 pro forma and pro forma as adjusted........... $      1  $    --     $    --
Common stock, $.0001 par value; 75,000,000
 shares authorized, 15,011,365 shares issued
 and outstanding, actual; 150,000,000 shares
 authorized, 24,717,365 shares issued and
 outstanding, pro forma; 150,000,000 shares
 authorized 30,717,365 shares issued and
 outstanding, pro forma as adjusted............        2         3           3
Additional paid-in capital.....................   38,915    38,915      88,085
Beneficial conversion feature..................   14,360    14,360      14,360
Warrants.......................................    2,472     2,472       2,472
Deferred stock compensation....................   (5,596)   (5,596)     (5,596)
Accumulated deficit............................  (30,392)  (30,392)    (30,392)
                                                --------  --------    --------
Total stockholders' equity.....................   19,762    19,762      68,932
                                                --------  --------    --------
  Total capitalization......................... $ 20,025  $ 20,025    $ 69,195
                                                ========  ========    ========
</TABLE>

  In addition to the 30,717,365 shares of common stock to be outstanding after
this offering, as of the closing of this offering and based on the number of
shares issued and options and warrants granted as of September 30, 1999, we
expect to have additional shares of common stock available for issuance under
the following plans and arrangements:

  . 12,130,500 shares issuable under our stock option plans, consisting of:

   . 9,287,198 shares underlying options outstanding at a weighted average
     exercise price of $0.82 per share, of which 5,024,303 were exercisable;
     and

   . 2,843,302 shares available for future issuance;

  . 875,000 shares issuable upon the exercise of warrants outstanding at a
    weighted average exercise price of $0.97 per share; and

  . 400,000 shares available for issuance under our 1999 Employee Stock
    Purchase Plan.

  Please read the capitalization table together with the sections of this
prospectus entitled "Selected Financial Data" and "Management's Discussion and
Analysis of Financial Condition and Results of Operations" and the financial
statements included in this prospectus.

                                       20
<PAGE>

                                    DILUTION

  As of September 30, 1999, our net tangible book value, on a pro forma basis
to give effect to the conversion of our preferred stock into common stock at
the closing of this offering, was $16.8 million, or $0.68 per share of common
stock. "Net tangible book value" per share represents the amount of our total
tangible assets reduced by the amount of our total liabilities, divided by the
number of shares of common stock outstanding. As of September 30, 1999, our net
tangible book value, on a pro forma basis to give effect to the sale of the
6,000,000 shares offered in this offering at an assumed initial public offering
price of $9.00 per share and after deducting the estimated underwriting
discount and offering expenses payable by us, would have been approximately
$2.16 per share. This represents an immediate increase of $1.48 per share to
existing stockholders and an immediate dilution of $6.84 per share to new
investors. The following table illustrates this per share dilution:

<TABLE>
<S>                                                                 <C>   <C>
Assumed initial public offering price per share....................       $9.00
 Pro forma net tangible book value per share as of September 30,
  1999............................................................. $0.68
 Increase per share attributable to new investors..................  1.48
                                                                    -----
Pro forma net tangible book value per share after the offering.....        2.16
                                                                          -----
Dilution per share to new investors................................       $6.84
                                                                          =====
</TABLE>

  The following table summarizes, as of September 30, 1999, on the pro forma
basis described above, the differences between the total consideration paid and
the average price per share paid by our existing stockholders and the new
investors with respect to the number of shares of common stock purchased from
us, based on an assumed initial public offering price of $9.00 per share:

<TABLE>
<CAPTION>
                                Shares Purchased     Total Consideration    Average
                              --------------------- ----------------------   Price
                                Number   Percentage   Amount    Percentage Per Share
                              ---------- ---------- ----------- ---------- ---------
     <S>                      <C>        <C>        <C>         <C>        <C>
     Existing stockholders... 24,717,365    80.5%   $29,507,010    35.3%     $1.19
     New investors...........  6,000,000    19.5     54,000,000    64.7       9.00
                              ----------   -----    -----------   -----
      Total.................. 30,717,365   100.0%   $83,507,010   100.0%
                              ==========   =====    ===========   =====
</TABLE>

  In addition to the 30,717,365 shares of common stock outstanding after this
offering, as of the closing of this offering and based on the number of shares
issued and options and warrants granted as of September 30, 1999, we expect to
have additional shares of common stock available for issuance under the
following plans and arrangements:

  . 12,130,500 shares issuable under our stock option plans, consisting of:

   . 9,287,198 shares underlying options outstanding at a weighted average
     exercise price of $0.82 per share, of which 5,024,303 were exercisable;
     and

   . 2,843,302 shares available for future issuance;

  . 875,000 shares issuable upon the exercise of warrants outstanding at a
    weighted average exercise price of $0.97 per share; and

  . 400,000 shares available for issuance under our 1999 Employee Stock
    Purchase Plan.

                                       21
<PAGE>

                            SELECTED FINANCIAL DATA

  The following selected financial data should be read in conjunction with
"Management's Discussion and Analysis of Financial Condition and Results of
Operations" and the financial statements and related notes included elsewhere
in this prospectus. The balance sheet data as of December 31, 1997 and 1998 and
the statement of operations data for the period from September 10, 1996
(inception) to December 31, 1996 and the years ended December 31, 1997 and 1998
have been derived from our audited financial statements and related notes
included elsewhere in this prospectus. The balance sheet data as of September
30, 1999 and the statement of operations data for the nine months ended
September 30, 1998 and 1999 are derived from our unaudited interim financial
statements included elsewhere in this prospectus. The balance sheet data as of
December 31, 1996 is derived from audited financial statements not included in
this prospectus. In management's opinion, the unaudited financial statements
have been prepared on substantially the same basis as the audited financial
statements and include all adjustments, consisting only of normal recurring
adjustments, necessary for a fair presentation of the results of operations for
such periods. Historical results are not necessarily indicative of the results
to be expected in the future, and the results of interim periods are not
necessarily indicative of results for the entire year.

<TABLE>
<CAPTION>
                          September 10,
                              1996
                           (inception)       Years Ended         Nine Months Ended
                           to December      December 31,           September 30,
                               31,      ----------------------  ---------------------
                              1996         1997        1998       1998        1999
                          ------------- ----------  ----------  ---------  ----------
                              (in thousands, except share and per share data)
<S>                       <C>           <C>         <C>         <C>        <C>
Statement of Operations
 Data:
Revenues................   $       --   $      426  $    3,588  $   2,591  $   13,941
Cost of revenues........           --          445       2,771      1,969      10,949
                           ----------   ----------  ----------  ---------  ----------
 Gross profit (loss)....           --          (19)        817        622       2,992
                           ----------   ----------  ----------  ---------  ----------
Operating expenses:
 Sales and marketing....           23          481         820        482       3,523
 Research and
  development...........           49          347         556        415       2,203
 General and
  administrative........           31          256         635        457       2,886
 Stock-based
  compensation..........          152           11         578        151       6,705
 Amortization of
  goodwill and
  intangibles...........           --           --          --         --         502
                           ----------   ----------  ----------  ---------  ----------
  Total operating
   expenses.............          255        1,095       2,589      1,505      15,819
                           ----------   ----------  ----------  ---------  ----------
Loss from operations....         (255)      (1,114)     (1,772)      (883)    (12,827)
Interest income
 (expense), net.........           --           (3)       (247)      (234)        187
                           ----------   ----------  ----------  ---------  ----------
Net loss................         (255)      (1,117)     (2,019)    (1,117)    (12,640)
Beneficial conversion
 feature of Series C
 convertible preferred
 stock..................           --           --          --         --      14,360
                           ----------   ----------  ----------  ---------  ----------
Net loss attributable to
 common stockholders....   $     (255)  $   (1,117) $   (2,019) $  (1,117) $  (27,000)
                           ==========   ==========  ==========  =========  ==========
Net loss per share--
 basic and diluted......   $    (0.07)  $    (0.13) $    (0.25) $   (0.13) $   (2.05)
                           ==========   ==========  ==========  =========  ==========
Weighted average shares
 outstanding............    3,795,714    8,457,464   8,186,127  8,591,365  13,074,428
                           ==========   ==========  ==========  =========  ==========
Pro forma net loss per
 share--basic and
 diluted................                            $    (0.25)            $    (1.56)
                                                    ==========             ==========
Weighted average shares
 used to compute
 pro forma net loss per
 share--basic and
 diluted................                             8,186,127             17,280,523
                                                    ==========             ==========
</TABLE>

<TABLE>
<CAPTION>
                                                    December 31,
                                                 --------------------  September
                                                 1996  1997    1998    30, 1999
                                                 ----  -----  -------  ---------
<S>                                              <C>   <C>    <C>      <C>
Balance Sheet Data:
Cash and cash equivalents....................... $ 27  $ 142  $   375   $16,520
Working capital.................................  (46)  (586)  (1,863)   14,743
Total assets....................................   52    262    1,444    27,492
Long-term debt .................................   --     65      232       263
Stockholders' equity (deficit):.................  (22)  (558)  (1,962)   19,762
</TABLE>

                                       22
<PAGE>

                       SELECTED PRO FORMA FINANCIAL DATA

  On March 25, 1999, we acquired Netranscend Software, Inc., a Java-based
business automation solutions software company. The acquisition was accounted
for using the purchase method of accounting and, accordingly, the purchase
price was allocated to the tangible and intangible assets acquired and
liabilities assumed on the basis of their fair values on the acquisition date.
The following unaudited pro forma statements of operations data reflect the
acquisition of Netranscend Software, Inc. as if the acquisition had occurred on
January 1, 1998. The pro forma statement of operations data may not be
indicative of the results of operations had the acquisition actually occurred
on January 1, 1998, nor do they purport to indicate our future results of
operations.

<TABLE>
<CAPTION>
                                                                  Nine Months
                                                     Year Ended      Ended
                                                    December 31, September 30,
                                                        1998         1999
                                                    ------------ -------------
                                                      (in thousands, except
                                                    share and per share data)
<S>                                                 <C>          <C>
Pro Forma Statement of Operations Data:
Revenues...........................................     $ 3,588     $ 13,941
Cost of revenues...................................       2,771       10,949
                                                     ----------   ----------
 Gross profit......................................         817        2,992
                                                     ----------   ----------
Operating expenses:
 Sales and marketing...............................         819        3,523
 Research and development..........................         557        2,203
 General and administrative........................         645        2,886
 Stock-based compensation..........................         578        6,705
 Amortization of goodwill and intangibles..........       1,003          752
                                                     ----------   ----------
  Total operating expenses.........................       3,602       16,069
                                                     ----------   ----------
Loss from operations...............................      (2,785)     (13,077)
Interest income (expense), net.....................        (247)         187
                                                     ----------   ----------
Net loss...........................................      (3,032)      12,890
Beneficial conversion feature of Series C
 convertible preferred stock.......................         --        14,360
                                                     ----------   ----------
Net loss attributable to common stockholders.......     $(3,032)    $(27,250)
                                                     ==========   ==========
Pro forma net loss per share--basic and diluted
 (1)...............................................     $ (0.30)    $  (1.99)
                                                     ==========   ==========
Weighted average shares used to compute pro forma
 net loss per share--basic and diluted (1).........  10,165,127   13,661,604
                                                     ==========   ==========
</TABLE>
- --------
(1) See Note B of Notes to Pro Forma Financial Information for a description of
    the method used to compute basic and diluted pro forma net loss per share.

                                       23
<PAGE>

                    MANAGEMENT'S DISCUSSION AND ANALYSIS OF
                 FINANCIAL CONDITION AND RESULTS OF OPERATIONS

  The following discussion of our financial condition and results of operations
should be read together with the financial statements and related notes that
are included later in this prospectus. This discussion contains forward-looking
statements that involve risks and uncertainties. Our actual results may differ
materially from those anticipated in these forward-looking statements as a
result of various factors, including those set forth under "Risk Factors" or in
other parts of this prospectus.

Overview

  We provide technology-based advertising and marketing services for companies
and advertising agencies that seek to optimize their Internet marketing
campaigns. Although we were incorporated in September 1996, we did not begin
offering our advertising campaign management services until April 1998. Before
April 1998, we operated under a different business model that generated
revenues primarily from the sale of advertising space on two Web sites formerly
operated by us that delivered sports and business news and information. We
decided to cease the operation of these sites because we determined that the
sites were not generating satisfactory operating results and because we
believed that our present business model represented a superior opportunity.
During the first half of 1998, we devoted most of our resources to developing
our new business plan and technology and establishing our technical and sales
organizations.

  In the second quarter of 1998, we began generating revenues from our
advertising campaign management services, and since the fourth quarter of 1998
we have derived substantially all of our revenues from this source. Our
campaign management services include planning the online campaign, coordinating
the online and offline portions of the campaign, purchasing and placing online
media, and tracking, analyzing and reporting the results of the media campaign.
In the second quarter of 1999, we began utilizing our mobile Java objects, or
MOJO, architecture to enhance our service offerings and expand our business. We
plan to broaden our revenue sources by leveraging the capabilities of our MOJO
architecture to offer message management services, which will allow advertisers
to integrate their internal business information into an online advertising
campaign and to tailor their advertising messages or offers in real time. To
date, we have not generated significant revenues from message management
services.

  We currently provide advertising campaign management services for a fixed
fee, which varies from client to client. This fee is principally based on the
extent of services provided and the direct cost of media placement. This cost
of purchasing advertising space on an Internet site is typically determined by
the cost per thousand impressions. Revenues from advertising campaign
management services are recognized in the period that advertising impressions
are delivered, or placed on an Internet site, provided that no significant
obligations on our part remain at the end of the period and the collection of
the resulting receivable is probable. Our obligations often include, for
instance, guarantees of a minimum number of impressions. To the extent that
significant obligations remain, we defer recognition of the corresponding
portion of the revenues until these obligations are met.

  In addition, we may generate revenues from clients obtained through or
referred to us by an ad agency. If an ad agency is used, we will usually bill
the ad agency for work done on behalf of the agency's clients, and the ad
agency will then be responsible for obtaining full payment from the client.
Sometimes, although less frequently, we will directly bill that ad agency's
client. To date, we have paid no referral fees to any ad agencies, nor have any
ad agencies paid referral fees to us, for referring clients. However, we may
pay and receive referral fees in the future.

  Cost of revenues consists primarily of the cost of procuring advertising
space on third-party Internet sites and, to a lesser extent, of the
telecommunications and other costs related to maintaining our ad servers at
third-party locations. These costs are recorded in the period that the
advertising impressions are delivered and the related revenues are recorded.
Currently, we purchase advertising space on Internet sites for a particular
media campaign. In the future, we may enter into purchase commitments to obtain
advertising space in bulk without a particular media campaign identified in
order to obtain more favorable pricing.

                                       24
<PAGE>

  To date, we have expensed all of our research and development costs in the
period in which we incur these costs. The period from achievement of
technological feasibility to the general availability of our software to
clients has been short, and therefore software development costs qualifying for
capitalization have been insignificant.

  In March 1999, we acquired Netranscend Software, Inc., a Java-based business
automation solutions software company, for a note payable of $430,000, due in
four annual installments beginning in March 2000, and 1,979,000 shares of
common stock. This acquisition was accounted for under the purchase method of
accounting. We recorded $3.0 million of goodwill and other identifiable
intangible assets in connection with this acquisition, which are being
amortized over a three-year period.

  We have a limited operating history upon which you may evaluate our business
and prospects. We incurred net losses of $255,000 in 1996, $1.1 million in
1997, $2.0 million in 1998 and $12.6 million in the first nine months of 1999.
At September 30, 1999, our accumulated deficit was $30.4 million. We anticipate
that we will incur additional operating losses for the foreseeable future.

  Since inception, we have incurred significant start-up expenses, including
development of our Web site and depreciation of computers and other office
equipment, which contributed to our initial losses. Our expenses through
September 30, 1999 were incurred primarily due to significant growth in
personnel costs in our sales and marketing, research and development, and
general and administrative functions which were not offset by a growth in
revenues. Our headcount increased from 7 as of September 30, 1998 to 109 as of
September 30, 1999. We believe this growth in personnel expenses has been
disproportionate to revenue growth because many of these employees were hired
to develop the corporate infrastructure. We expect that in the future, the
growth in our expenses will be more proportional to the growth in our business
and our revenues. We believe that while our operating expenses will increase in
absolute dollars, as we grow our business they will decrease as a percentage of
revenues.

Results of Operations

  The following table sets forth our statement of operations data expressed as
a percentage of revenues:

<TABLE>
<CAPTION>
                                                              Nine Months
                                                                 Ended
                                             Years Ended       September
                                             December 31,         30,
                                             --------------   --------------
                                              1997    1998    1998     1999
                                             ------   -----   -----   ------
<S>                                          <C>      <C>     <C>     <C>
Revenues....................................  100.0 % 100.0 % 100.0 %  100.0 %
Cost of revenues............................  104.6    77.2    76.0     78.5
                                             ------   -----   -----   ------
 Gross profit (loss)........................   (4.6)   22.8    24.0     21.5
                                             ------   -----   -----   ------
Operating expenses:
 Sales and marketing........................  112.9    22.8    18.6     25.3
 Research and development...................   81.5    15.5    16.0     15.8
 General and administrative.................   60.0    17.8    17.6     20.7
 Stock-based compensation...................    2.6    16.1     5.9     48.1
 Amortization of goodwill and intangibles...     --      --      --      3.6
                                             ------   -----   -----   ------
  Total operating expenses..................  257.0    72.2    58.1    113.5
                                             ------   -----   -----   ------
Loss from operations........................ (261.6)  (49.4)  (34.1)   (92.0)
Interest income (expense), net..............   (0.6)   (6.9)   (9.0)     1.3
                                             ------   -----   -----   ------
Net loss.................................... (262.2)  (56.3)  (43.1)   (90.7)
Beneficial conversion feature of Series C
 convertible preferred stock................     --      --      --    103.0
                                             ------   -----   -----   ------
Net loss attributable to common
 stockholders............................... (262.2)% (56.3)% (43.1)% (193.7)%
                                             ======   =====   =====   ======
</TABLE>

Nine Months Ended September 30, 1999 and 1998

  Revenues. Revenues increased to $13.9 million for the nine months ended
September 30, 1999 from $2.6 million for the nine months ended September 30,
1998. The period-to-period increase was primarily due to our

                                       25
<PAGE>

commencement of selling advertising campaign management services to a broad set
of advertisers, including advertising agencies, in April 1998. In the first
nine months of 1999, substantially all of our revenues consisted of advertising
fees received for providing advertising campaign management services. In the
first nine months of 1998, our revenues were primarily derived from the sale of
advertising on our Internet content sites.

  In the nine months ended September 30, 1999, three of our clients represented
approximately 38% of our revenues, and in the nine months ended September 30,
1998, four of our clients represented approximately 80% of our revenues.

  Cost of Revenues. Cost of revenues increased to $10.9 million, or 78.5% of
revenues, for the nine months ended September 30, 1999 from $2.0 million, or
76.0% of revenues, for the nine months ended September 30, 1998. The increase
in cost of revenues in the 1999 period was primarily due to the increase in our
revenues. The cost of revenues in the nine months ended September 30, 1999
comprised primarily media placement costs, while the cost of revenues in the
nine months ended September 30, 1998 consisted primarily of the cost of
maintaining our Internet content sites.

Operating Expenses

  Sales and Marketing. Sales and marketing expenses consist primarily of
compensation expenses, including salaries, commissions and related payroll
expenses, recruiting costs, and marketing expenses, including those expenses
associated with customer service and support. Sales and marketing expenses
increased to $3.5 million, or 25.3% of revenues, for the nine months ended
September 30, 1999 from $482,000, or 18.6% of revenues, for the nine months
ended September 30, 1998. The dollar increase in sales and marketing expenses
during the 1999 period was primarily due to the significant growth of our sales
and marketing organization in 1999 as we focused on selling advertising
campaign management services. The number of sales and marketing personnel
increased from 6 as of September 30, 1998 to 53 as of September 30, 1999. We
expect that sales and marketing expenses will continue to increase in dollars
and, in the near term, increase as a percentage of revenues.

  Research and Development. Research and development expenses consist primarily
of compensation and related expenses for our internal development staff and
fees for contractor services. Research and development expenses increased to
$2.2 million, or 15.8% of revenues, for the nine months ended September 30,
1999 from $415,000, or 16.0% of revenues, for the nine months ended September
30, 1998. This dollar increase in research and development expenses was due
primarily to an increase in the number of development engineers in our research
and development organization. The number of development engineers increased
from 1 as of September 30, 1998 to 36 as of September 30, 1999. The decrease in
research and development expenses as a percentage of revenues was primarily due
to the significant growth in revenues. We expect to continue to spend
significant amounts on research and development as we continue to develop and
upgrade our technology. Accordingly, we expect that research and development
expenses will continue to increase in dollars and, in the near term, increase
as a percentage of revenues.

  General and Administrative. General and administrative expenses consist
primarily of compensation and related expenses and fees for contractor
services. General and administrative expenses increased to $2.9 million, or
20.7% of revenues, for the nine months ended September 30, 1999 from $457,000,
or 17.6% of revenues, for the nine months ended September 30, 1998. The dollar
increase in general and administrative expenses was due primarily to the hiring
of general and administrative personnel. We had no general and administrative
personnel as of September 30, 1998 and 20 persons as of September 30, 1999. The
decrease in general and administrative expenses as a percentage of revenues was
primarily due to the significant growth in revenues. We expect that general and
administrative expenses will continue to increase in dollars in the future,
reflecting the additional costs associated with increasing our infrastructure
and headcount as we grow and the costs of being a public company and, in the
near term, increase as a percentage of revenues.

  Stock-based Compensation. Stock-based compensation expense increased to $6.7
million, or 48.1% of revenues, for the nine months ended September 30, 1999
from $151,000, or 5.9% of revenues, for the nine

                                       26
<PAGE>

months ended September 30, 1998. For accounting purposes, we recognize stock-
based compensation in connection with the issuance of shares of our common
stock and the granting of options or warrants to purchase our common stock to
employees and consultants with purchase or exercise prices that are less than
the deemed fair market value at the grant date. Stock-based compensation
related to the issuance of shares of common stock has been expensed in the
period in which the common stock was issued. Stock-based compensation related
to the issuance of options and warrants to purchase common stock is being
amortized over the vesting period of the stock options through 2003. Total
deferred stock compensation as of September 30, 1999 was $5.6 million. These
deferred amounts and the related amortization charges will increase if we
record further deferred stock compensation in future periods.

  Amortization of Goodwill and Intangible Assets. Amortization expense was
$502,000, or 3.6% of revenues, for the nine months ended September 30, 1999,
due to the amortization of goodwill and intangible assets recorded in
connection with our acquisition of Netranscend Software, Inc. in March 1999. We
recorded no goodwill amortization expense for the first nine months of 1998. We
expect to recognize $251,000 of amortization expense for this transaction in
each quarter through the first quarter of 2002.

  Interest Income (Expense), Net. Interest income, net was $187,000 for the
nine months ended September 30, 1999, representing primarily interest earned on
the $24.1 million of cash and cash equivalents we generated in the period from
private placements of convertible preferred stock. The net interest expense of
$234,000 in the nine months ended September 30, 1998 was primarily due to the
beneficial conversion feature of a note payable to stockholders.

  Net Loss. Net loss was $12.6 million for the nine months ended September 30,
1999, and $1.1 million for the nine months ended September 30, 1998. The
increase in net loss of $11.5 million from the 1998 period to the 1999 period
was primarily due to the increase in operating expenses of $14.3 million from
the 1998 period to the 1999 period. In particular, stock-based compensation
increased $6.6 million from the 1998 period to the 1999 period.

  Beneficial Conversion Feature of the Series C Convertible Preferred Stock. In
August 1999, Mediaplex issued 4,000,000 shares of Series C convertible
preferred stock at a purchase price of $3.59 per share. These shares are
convertible into shares of common stock on a one-for-one basis. Because the
conversion price is less than the low end of the price range for the
anticipated initial public offering, the Series C preferred stock is deemed to
have an embedded beneficial conversion feature. This feature allows the holders
to acquire common stock at a purchase price below its deemed fair value. The
amount of the discount assigned to the beneficial conversion feature is limited
to the amount of the proceeds. Consequently, the issuance and sale of the
Series C preferred stock resulted in a beneficial conversion feature of
$14,360,000, which has been reflected as a preferred dividend in our statement
of operations in the third quarter of 1999.

Years Ended December 31, 1998, 1997 and 1996

  Revenues. Revenues were $3.6 million in 1998 and $426,000 in 1997. We did not
have any revenues in 1996. The increase in revenues from 1997 to 1998 was
primarily due to the commencement of selling advertising campaign management
services in April 1998. In 1997, we were selling advertising space on our
Internet content sites under our prior business model. In 1998, we began
providing our advertising campaign management services and increased our sales
force, resulting in significant revenue growth in 1998.

  Cost of Revenues. Total cost of revenues was $2.8 million, or 77.2% of
revenues, in 1998 and $445,000, or 104.6% of revenues, in 1997. The dollar
increase in cost of revenues was primarily due to the increase in revenues from
1997 to 1998. The decrease in cost of revenues as a percentage of revenues in
1998 as compared to 1997 was primarily due to the commencement of selling
advertising campaign management services.

                                       27
<PAGE>

Operating Expenses

  Sales and Marketing. Sales and marketing expenses were $820,000, or 22.8% of
revenues, in 1998, $481,000, or 112.9% of revenues, in 1997, and $23,000 in
1996. The dollar increases in sales and marketing expenses from 1996 to 1997,
and from 1997 to 1998 were primarily due to increases in the number of sales
personnel. The decrease in sales and marketing expenses as a percentage of
revenues was primarily due to the rate of increase in revenues in 1998.

  Research and Development. Research and development expenses were $556,000, or
15.5% of revenues, in 1998, $347,000, or 81.5% of revenues, in 1997, and
$49,000 in 1996. The dollar increases in research and development expenses from
1996 to 1997, and from 1997 to 1998 were primarily due to the increases in the
number of development engineers we employed. The decrease in research and
development expenses as a percentage of revenues was primarily due to the rate
of increase in revenues in 1998.

  General and Administrative. General and administrative expenses were
$636,000, or 17.8% of revenues, in 1998, $256,000, or 60.0% of revenues, in
1997, and $31,000 in 1996. The dollar increases in general and administrative
expenses from 1996 to 1997, and from 1997 to 1998 were primarily due to the
increases in the number of administrative personnel and outside administrative
services costs. The decrease in general and administrative expenses as a
percentage of revenues was primarily due to the rate of increase in revenues in
1998.

  Stock-based Compensation. Stock-based compensation expense was $578,000 in
1998, $11,000 in 1997 and $152,000 in 1996.

  Interest Income (Expense), Net. Net interest expense was $247,000 in 1998 and
$3,000 in 1997. There was no interest income or expense in 1996.

  Net Loss. Net loss was $2.0 million in 1998 and $1.1 million in 1997. The
increase in net loss of $900,000 from 1997 to 1998 is primarily due to the
increase in cost of revenues of $2.3 million and the increase in operating
expenses of $1.5 million from 1997 to 1998, which increases were partially
offset by an increase in revenues of $3.2 million from 1997 to 1998.

                                       28
<PAGE>

Quarterly Results of Operations

  The following table presents statement of operations data for the four
quarters of 1998 and first three quarters of 1999. We believe that this
unaudited information has been prepared on the same basis as the audited annual
financial statements and includes all adjustments, consisting only of normal
recurring adjustments, necessary for a fair presentation of the unaudited
financial information for the quarters presented. You should read this in
conjunction with our financial statements, including the accompanying notes,
included elsewhere in this prospectus.

<TABLE>
<CAPTION>
                                                 Three Months Ended
                          -----------------------------------------------------------------
                                                                           June
                          March 31, June 30, Sept. 30, Dec. 31, March 31,   30,     Sept.
                            1998      1998     1998      1998     1999     1999    30, 1999
                          --------- -------- --------- -------- --------- -------  --------
                                                   (in thousands)
<S>                       <C>       <C>      <C>       <C>      <C>       <C>      <C>
Statements of Operations
Data:
Revenues................    $ 586    $ 935    $1,069    $  997   $ 1,634  $ 5,689  $  6,618
Cost of revenues........      480      733       756       802     1,340    4,421     5,187
                            -----    -----    ------    ------   -------  -------  --------
 Gross profit...........      106      203       313       195       294    1,268     1,431
                            -----    -----    ------    ------   -------  -------  --------
Operating expenses:
 Sales and marketing....      193      201        87       338       543    1,104     1,876
 Research and
  development...........      125       95       195       140       308      507     1,388
 General and
  administrative........      117      207       132       180       456      626     1,804
 Stock-based
  compensation..........       --      151        --       427     1,953    1,338     3,414
 Amortization of
  goodwill and
  intangibles...........       --       --        --        --        --      251       251
                            -----    -----    ------    ------   -------  -------  --------
  Total operating
   expenses.............      435      655       414     1,085     3,260    3,826     8,733
                            -----    -----    ------    ------   -------  -------  --------
Loss from operations....     (329)    (452)     (101)     (890)   (2,966)  (2,558)   (7,302)
Interest income
 (expense), net.........       (1)      (1)     (230)      (15)        1       12       173
                            -----    -----    ------    ------   -------  -------  --------
Net loss................     (330)    (453)     (331)     (905)   (2,965)  (2,546)   (7,129)
Beneficial conversion
 feature of Series C
 preferred stock........       --       --        --        --        --       --    14,360
                            -----    -----    ------    ------   -------  -------  --------
Net loss attributable to
 common stockholders....    $(330)   $(453)   $ (331)   $ (905)  $(2,965) $(2,546) $(21,489)
                            =====    =====    ======    ======   =======  =======  ========
</TABLE>

<TABLE>
<CAPTION>
                                                  Three Months Ended
                          ----------------------------------------------------------------------
                          March 31, June 30,  Sept. 30, Dec. 31,  March 31,  June 30,  Sept. 30,
                            1998      1998      1998      1998      1999       1999      1999
                          --------- --------  --------- --------  ---------  --------  ---------
<S>                       <C>       <C>       <C>       <C>       <C>        <C>       <C>
As a Percentage of
 Revenues:
Revenues................    100.0 %  100.0 %    100.0 %  100.0 %    100.0 %   100.0 %    100.0 %
Cost of revenues........     81.9     78.3       70.7     80.4       82.0      77.7       78.4
                            -----    -----      -----    -----     ------     -----     ------
 Gross profit...........     18.1     21.7       29.3     19.6       18.0      22.3       21.6
                            -----    -----      -----    -----     ------     -----     ------
Operating expenses:
 Sales and marketing....     33.0     21.5        8.1     33.9       33.2      19.4       28.3
 Research and
  development...........     21.3     10.2       18.3     14.1       18.9       8.9       21.0
 General and
  administrative........     19.9     22.2       12.3     18.0       27.9      11.0       27.2
 Stock-based
  compensation..........       --     16.2         --     42.8      119.6      23.6       51.6
 Amortization of
  goodwill and
  intangibles...........       --       --         --       --         --       4.4        3.8
                            -----    -----      -----    -----     ------     -----     ------
  Total operating
   expenses.............     74.2     70.1       38.7    108.8      199.6      67.3      131.9
                            -----    -----      -----    -----     ------     -----     ------
Loss from operations....    (56.0)   (48.4)      (9.4)   (89.3)    (181.6)    (45.0)    (110.3)
Interest income
 (expense), net.........     (0.2)    (0.1)     (21.5)    (1.5)       0.1       0.2        2.6
                            -----    -----      -----    -----     ------     -----     ------
Net loss................    (56.2)   (48.5)     (30.9)   (90.8)    (181.5)    (44.8)    (107.7)
Beneficial conversion
 feature of Series C
 preferred stock........       --       --         --       --         --        --      217.0
                            -----    -----      -----    -----     ------     -----     ------
Net loss attributable to
 common stockholders....    (56.2)%  (48.5)%    (30.9)%  (90.8)%   (181.5)%   (44.8)%   (324.7)%
                            =====    =====      =====    =====     ======     =====     ======
</TABLE>


                                       29
<PAGE>

  Due to the early stage of our company and the commencement of selling
advertising campaign management services in April 1998, period-to-period
comparisons of our historical operating results should not be relied upon as
indicative of future performance. During the second and third quarters of 1998,
our results reflect the transition from our prior business of managing Internet
content sites to our advertising campaign management services business. The
quarter ended September 30, 1998 was the last quarter in which we generated
revenues from our prior business model. Beginning in the fourth quarter of
1998, our financial performance solely reflected our current advertising
campaign management services.

  The increases in sales and marketing expenses, research and development
expenses, and general and administrative expenses from the quarter ended
December 31, 1998 through the quarter ended June 30, 1999 are primarily due to
increased compensation and related expenses as a result of the increased
headcount required to support the growth in advertising campaign management
services revenues.

  The stock-based compensation expense for the quarter ended June 30, 1998
represented the non-cash expense related to the issuance of shares of our
common stock for services rendered. The stock-based compensation expense for
the quarters ended December 31, 1998 and March 31, 1999 represented expense for
the issuance of shares in exchange for services, and the amortization of
deferred stock compensation recorded for options granted to employees and
consultants to purchase common stock with exercise prices that were less than
the deemed fair market value at the grant date. The stock-based compensation
expense for the quarters ended June 30 and September 30 1999 consisted solely
of amortization of the deferred stock compensation recorded for options and
warrants granted to employees to purchase common stock at exercise prices that
were less than the deemed fair market value at the grant date.

  Although we have experienced revenue growth in recent periods, we anticipate
that we will incur operating losses for the foreseeable future due to the high
level of planned operating and capital expenditures.

Liquidity and Capital Resources

  From our inception in September 1996 through September 1999, we financed our
operations primarily through the private placement of preferred stock, which
has generated net proceeds of $24.1 million. As of September 30, 1999, we had
$16.5 million in cash and cash equivalents.

  Net cash used in (provided for) operating activities in the nine months ended
September 30, 1999 and 1998, the years ended December 31, 1998 and 1997 and the
period from September 10, 1996 (inception) through December 31, 1996, was $6.1
million, $(166,000), $240,000, $150,000 and $28,000, respectively. Net cash
used in operating activities in each of these periods was primarily the result
of net losses before non-cash charges and increases in accounts receivable,
offset by increases in accrued liabilities and deferred revenues.

  Net cash used in investing activities in the nine months ended September 30,
1999 and 1998, the years ended December 31, 1998 and 1997 and the period from
September 10, 1996 (inception) through December 31, 1996, was $2.0 million,
$44,000, $79,000, $70,000 and $24,000, respectively. Net cash used in investing
activities in all periods presented was due principally to the acquisition of
computer equipment and software.

  Net cash provided by financing activities in the nine months ended September
30, 1999 and 1998, the years ended December 31, 1998 and 1997 and the period
from September 10, 1996 (inception) through December 31, 1996, was $24.2
million, $290,000, $551,000, $335,000 and $80,000, respectively. Net cash
provided by financing activities in all periods was primarily due to sales of
shares of our common stock and, in the nine months ended September 30, 1999,
our preferred stock, as well as in 1998 and the nine months ended September 30,
1998, funds borrowed from stockholders under notes payable that bore interest
at 6% per annum. A portion of these notes payable were paid off in the six
months ended June 30, 1999. We currently have no other borrowings.

  Although we have no material commitments for capital expenditures, we
anticipate an increase in the rate of capital expenditures consistent with our
anticipated growth in operations, infrastructure and personnel. We

                                       30
<PAGE>

believe that the net proceeds from this offering, combined with our cash and
cash equivalents, will be sufficient to meet our anticipated liquidity needs
for working capital and capital expenditures for at least twelve months from
the date of this prospectus. We estimate that, if we limit our growth, without
this offering our current resources would be sufficient to fund our operations
through the next twelve months. After the next twelve months, we expect to
continue to incur net losses for the foreseeable future and may need additional
funds to expand or to meet all of our operating needs. Our forecast of the
period of time through which our financial resources will be adequate to
support operations is a forward-looking statement that involves risks and
uncertainties, and actual results could vary materially as a result of the
factors described above. If we require additional capital resources to grow our
business internally or to acquire complementary technologies and businesses, we
may seek to sell additional equity or debt securities or secure a bank line of
credit. The sale of additional equity or convertible debt securities could
result in additional dilution to our stockholders. We cannot assure you that
any financing arrangements will be available in amounts or on terms acceptable
to us.

Market Risk Disclosure

  The following discusses our exposure to market risk related to changes in
foreign currency exchange rates and interest rates. This discussion contains
forward-looking statements that are subject to risks and uncertainties. Actual
results could vary materially as a result of a number of factors including
those set forth in the risk factors section of this prospectus.

  Foreign Currency Exchange Rate Risk. To date, we have not had any revenues
from international operations. All of our recognized revenues have been
denominated in U.S. dollars from clients in the United States. We expect,
however, that some future revenues may be derived from international markets
and may be denominated in the currency of the applicable market. As a result,
our operating results may become subject to significant fluctuations in the
exchange rates of foreign currencies. Furthermore, to the extent that we engage
in international sales denominated in U.S. dollars, an increase in the value of
the U.S. dollar relative to foreign currencies could make our products less
competitive in international markets. Although we expect to monitor our
exposure to currency fluctuations as we expand into international markets and,
when appropriate, may use financial hedging techniques in the future to
minimize the effect of these fluctuations, exchange rate fluctuations could
harm our financial results in the future.

  Interest Rate Risk. As of September 30, 1999, we had cash and cash
equivalents of $16.5 million, which consisted of cash and highly liquid short-
term investments. Our short-term investments will decline in value by an
immaterial amount if market interest rates increase. Declines of interest rates
over time will, however, reduce our interest income from our short-term
investments.

Recent Accounting Pronouncements

  In March 1998, the Accounting Standards Executive Committee, or ASEC, issued
Statement of Position 98-1, "Accounting for the Costs of Computer Software
Developed or Obtained for Internal Use." SOP 98-1 provides guidance on when
costs related to software developed or obtained for internal use should be
capitalized or expensed. SOP 98-1 is effective for transactions entered into
for fiscal years beginning after December 15, 1998. The adoption of this
statement did not have a material effect upon our statement of operations.

  In April 1998, the ASEC issued SOP 98-5, "Reporting on the Costs of Start-Up
Activities." SOP 98-5 requires the cost of start-up activities, including
organization costs, to be expensed as incurred. The adoption of this statement
did not have a material effect upon our statement of operations.

  In June 1998, the Financial Accounting Standards Board issued Statement of
Financial Accounting Standards No. 133, "Accounting for Derivative Instruments
and Hedging Activities," which requires companies to record derivative
financial instruments on the balance sheet as assets or liabilities, measured
at fair value. Gains or losses resulting from changes in the values of those
derivatives would be accounted for depending on

                                       31
<PAGE>

the use of the derivative and whether it qualifies for hedging accounting. The
key criterion for hedge accounting is that the hedging relationship must be
highly effective in achieving offsetting changes in fair value or cash flows.
SFAS No. 133 is effective for all fiscal quarters of all fiscal years beginning
after June 15, 1999. We do not anticipate that this statement will have a
material effect upon our statement of operations.

  In December 1998, the American Institute of Certified Public Accountants
issued SOP 98-9, "Modification of SOP 97-2, Software Revenue Recognition, with
Respect to Certain Transactions." SOP 98-9 amends SOP 97-2 and SOP 98-4 by
extending the deferral of the application of certain provisions of SOP 97-2
amended by SOP 98-4 through fiscal years beginning on or before March 15, 1999.
All other provisions of SOP 98-9 are effective for transactions entered into in
fiscal years beginning after March 15, 1999. We do not anticipate that the
adoption of these statements will have a material effect upon our statement of
operations.

Year 2000 Compliance

  Many currently installed computer systems and software products worldwide are
coded to accept only two-digit entries to identify a year in the date code
field. Consequently, on January 1, 2000, many of these systems could fail or
malfunction because they are not able to distinguish between the year 1900 and
the year 2000. Accordingly, many companies, including ourselves and our
clients, potential clients, vendors and business and marketing alliances, may
need to upgrade their systems to comply with applicable year 2000 requirements.

  Because we and our clients depend, to a very substantial degree, upon the
proper functioning of computer systems, a failure of these systems to correctly
recognize dates beyond December 31, 1999 could disrupt operations. Any
disruptions could harm our business. Additionally, our failure to provide Year
2000 compliant solutions to our clients could result in financial loss,
reputational harm and legal liability to us.

  Substantially all of our computer equipment and software was purchased in the
past twelve months. As a result, we believe that this software is generally
year 2000 compliant, meaning that the use or occurrence of dates on or after
January 1, 2000 will not materially affect the performance of this software or
the ability of this software to correctly create, store, process and output
data involving dates.

  We typically use industry-standard third-party hardware and software. We have
not, to date, sought assurances from our suppliers or customers that their
products or systems are year 2000 compliant, but instead have relied on
publicly available information in some cases as to their products or computer
systems being year 2000 compliant. We also generally do not have any
contractual rights with these providers if their software or hardware fails to
function due to year 2000 issues. If these failures do occur, we may incur
unexpected expenses to remedy any problems, including purchasing replacement
hardware and software.

  Because our computer equipment and software is substantially new, we have not
engaged any third parties to independently verify our year 2000 readiness, nor
have we assessed potential costs associated with year 2000 risks or made any
contingency plans to address these risks. We have not, to date, incurred any
costs separate from the expenditures for acquiring new computer equipment and
infrastructure to address year 2000 issues. In addition, we do not anticipate
incurring any costs directly related to addressing year 2000 issues because,
based on the relatively new installation of our computer equipment and systems,
we believe that our computer equipment and systems are year 2000 compliant.
Further, we have not deferred any of our ongoing development efforts to address
year 2000 issues. Unanticipated costs associated with any year 2000 compliance
could materially harm our quarterly and annual results of operations.

  We are currently implementing a new accounting and management reporting
system for business reasons unrelated to the year 2000 issue. We have been
assured that our new system is year 2000 compliant by the vendor. If any of our
vendors' representations regarding their products are not accurate, or if we
encounter unknown year 2000 problems relating to the interaction of our
systems, we could incur significant expenses to resolve these issues or damages
resulting from a failure of our systems to perform correctly. For example, if
our

                                       32
<PAGE>

accounting system fails to record our transactions properly, we would need to
devote additional staff or hire a third party to correct the problem, could
lose important data and would have difficulty planning without accurate
financial information.

  We depend on the uninterrupted availability of the Internet infrastructure to
conduct our business. We rely on the continued operations of the computer
systems of our vendors, in particular, those vendors whose Web sites host our
clients' advertisements, and the computer systems of our clients. The
successful implementation of our media messaging services for our clients
requires our technology to interact with our clients' internal business
computer systems. If our clients' computer systems fail because their systems
are not year 2000 compliant, we will be unable to fully deliver the services
that our clients may have requested, and our revenues would decrease. In
addition, the failure of a client to receive the performance reports of the
advertisements served due to a failure of its computer systems would hamper the
effectiveness of our services for that client. Interruptions in the Internet
infrastructure affecting us, our clients or our vendors, or failure of the year
2000 compliance efforts of one or more of our clients or vendors, could harm
our ability to generate revenue and, if severe, our business, results of
operations and financial condition. In the worst case, any failure in the
Internet infrastructure could prevent us from serving advertisements for our
clients for a period of time, resulting in lower revenues and client
complaints. We currently do not have any special contingency plans for a
lengthy Internet infrastructure failure due to year 2000 issues.

  In the event we discover year 2000 problems in our products or internal
systems, we will endeavor to resolve these problems by making modifications to
our products or systems or purchasing new systems, on a timely basis. In
addition, the effect of year 2000 issues on our clients generally, or on our
banks, the stock markets and other infrastructure functions, such as our
telephone system, electrical systems and water supplies, is unknown. We cannot
assure you that our systems will be year 2000 compliant. We may incur
unexpected material expenses or liability relating to the year 2000 problem.

                                       33
<PAGE>

                                    BUSINESS

  We provide technology-based services that enable companies to integrate their
internal business information, such as inventory and price levels, into their
online advertising activities to deliver customized messages and offers to Web
site visitors. Our services encompass planning, executing, monitoring and
analyzing Web-based campaigns, and are based upon proprietary technology,
tradenamed "MOJO," which stands for "mobile Java objects." Our technology
allows companies to change the content of Internet messages and offers in real
time, or virtually instantaneously, in response to changes in their underlying
business variables, such as inventory levels, product pricing and customer
data. For example, an airline can continually update its advertising messages
across all Web sites in a particular campaign to reflect changes in seat
availability and prices.

Industry Background

The Internet as an Advertising Medium for Direct Marketing and Branding

  The Internet is rapidly becoming an important advertising medium for direct
marketing and product branding. Forrester Research, Inc. anticipates that U.S.
online advertising spending will grow from $2.8 billion in 1999 to $17.2
billion in 2003, driven by a number of factors, including the growing online
population, the acceleration of e-commerce, or commerce conducted over the
Internet, and the advancement of online marketing technologies. According to
International Data Corporation, the U.S. online population is projected to grow
from 80.8 million in 1999 to 177.0 million by 2003, and U.S. e-commerce
spending is projected to increase from $74.4 billion in 1999 to $707.9 billion
by the end of 2003.

  To date, the major spenders in online advertising have been Internet,
computer and technology companies and financial institutions. We believe other
advertisers, who have historically used more traditional media, are
increasingly becoming attracted to the Internet because of its global reach,
potential to enable one-to-one marketing and ability to track and measure
campaign results in real time. Advertisers are beginning to recognize the
effectiveness of the Internet to build long-term brand awareness, perform
valuable market testing, and facilitate immediate trial and sales of products
and services. In contrast to traditional, or off-line advertising, the
interactive nature of the Internet gives companies the ability to send
advertising messages to consumers and enables consumers to immediately respond
to the advertising. Furthermore, the Internet enhances client-specific
marketing campaigns to promote customer retention and loyalty.

  Despite the emergence of the Internet as a medium for advertising,
expenditures for online advertising represent only a small portion of all media
spending. Forrester Research, Inc. estimates that by 2003, U.S. total media
spending will reach approximately $260.6 billion, of which the online component
of $17.2 billion will represent only 6.6%. We believe online media spending has
the potential to capture a larger portion of total media spending as new
technologies improve the effectiveness of online advertising and attract more
traditional media advertisers to the Internet.

  We believe the rapid growth of e-commerce has changed the nature and pace of
business operations and competition. Companies are increasingly realizing the
importance of using the Internet to manage and transact business, and
communicate with consumers, clients, suppliers and partners, far beyond the
simple sale of products and services over the Internet. In addition, we believe
companies are increasingly leveraging their significant financial and technical
investments in software applications that manage and store critical business
information, such as business resource planning and supply and distribution
management systems.

The Challenges of Online Advertising

  An effective online marketing campaign requires a wide range of
implementation, management and technology expertise in campaign development,
advertising execution and results analysis. The real-time delivery, measurement
and analysis of multiple advertising campaigns encompassing thousands of Web
sites is complex and difficult to execute and manage. We believe traditional
advertising agencies and most companies

                                       34
<PAGE>

typically do not have the expertise in the Internet medium to address these
delivery and management requirements.

  The increase in online advertising spending has heightened expectations for
more effective advertising campaigns and improved return on investment of
advertising dollars spent. The standard benchmarks to measure the impact of an
advertising campaign are banner impressions, viewer click-through rates to
advertisers' sites from online messages, and conversion rates, which are the
percentage of consumers who complete a purchase or other transaction. We
believe click-through rates have been declining as advertisers increasingly
compete for the attention of online consumers, and as a result, companies are
searching for more effective advertising messaging techniques in order to
increase click-through and conversion rates.

  To date, online advertising has not achieved effective "one-to-one"
marketing, which entails delivery of the right message to the right consumer in
real time. Ideally, advertisers seek to identify potential customers most
likely to purchase their products, send them a message tailored to their
individual preferences, and do so at a time when they are most likely to make a
purchase decision. Most current technologies are focused on identifying the
right consumer based on their demographic, geographic or consumer preference
data. Identifying the right consumer, however, represents only one component of
true one-to-one marketing. The ability to send the right message in real time
remains a significant challenge.

  Sending a customized message in real time would enable companies to use the
Internet as an effective online marketing and sales channel. The right message
includes appropriate product information for a particular consumer based on the
existing status of a company's underlying business variables including, for
example, product pricing and availability. In order to achieve this, companies
must access and integrate their existing business information into the online
advertising process, enabling them to incorporate their business information in
targeted messages and turn an advertisement into an effective marketing tool.
For example, a hotel with excess availability in New York City would seek to
advertise discounts to consumers booking flights to New York.

  We believe that there is a significant opportunity for a vendor who can
provide a comprehensive, technology-based solution for online advertising
campaigns. We believe that this solution must provide the following key
capabilities:

  . the expertise to manage and execute all aspects of online marketing
    campaigns;

  . the ability to accumulate valuable data on customer behavior;

  . the ability to perform detailed return on advertising investment analyses
    in a timely fashion;

  . the ability to customize messages and offers in real time; and

  . the ability to integrate important business data, such as product and
    pricing information, into online advertising message content.

Solution

  We provide technology-based services that enable companies to deliver
customized online advertising messages and offers that reflect their internal
business data in real time. Our MOJO technology allows companies to adjust
their online advertising virtually instantaneously in response to changes in
their underlying business variables, such as inventory levels, product pricing
and customer data. Our services encompass planning, executing, monitoring and
analyzing online marketing campaigns. Our clients either develop the
advertisements themselves, or contract with an advertising agency to perform
the creative development of the ad campaign. We believe the wide range of
services we offer will enable advertisers to deliver more effective online
campaigns and improve their return on advertising investment.

  Our solution includes the following benefits:

  . Comprehensive Online Advertising Campaigns. Using our technology platform
    and expertise in online advertising, we provide a range of advertising
    services that optimize online campaigns, including strategic planning,
    execution of media buys, ad serving and reporting capabilities. We serve
    online advertisements that have been designed and created by our clients
    or their advertising agencies.

                                       35
<PAGE>


  . Real-time Tracking and Measuring Campaign Results. For any given
    campaign, we monitor its effectiveness by tracking multiple statistics
    that measure campaign performance, including click-through and conversion
    rates, as well as revenues derived from these conversions. Based on the
    results of this monitoring, campaigns can be automatically or manually
    modified in real time to maximize the return on advertising investment.

  . Message Re-targeting. We use Internet browser-based tracking tools to
    capture and analyze data on consumer behavior and site visitation
    patterns. We use this data to refine future messages to consumers whom we
    have previously identified.

  . Real-time Messaging Capabilities. We have the ability to change the
    content of online advertisements in real time. This enables a company to
    tailor its marketing messages based on consumer profiles as well as
    predefined parameters or business rules, such as product rotations or
    pricing. We also enable a company to test advertising graphics, messages
    and sites, and adjust them in real time based on the effectiveness of
    these graphics, messages and sites.

  . Integration of Internal Business Information. Our MOJO technology enables
    us to integrate online advertising campaigns with a client's internal
    business information, allowing us to dynamically tailor and deliver
    advertisements based on a consumer's profile and on a client's inventory,
    pricing or other underlying business variables at a particular point in
    time. We believe that this integration leads to more effective messaging,
    increased sales and improved inventory management by our client. In this
    sense, we believe that our technology will not only be used to report on,
    but also to improve, return on investment results.

Strategy

  Our objective is to become the leading provider of technology-enabled
marketing solutions. Our strategy includes the following key elements:

  . Target Global 1000 and e-Commerce Companies. We can provide significant
    benefits to large companies that require online advertising management
    and technology expertise for the Internet and have made a significant
    investment in software applications which manage and store critical
    internal business information. We also intend to target companies that
    rely on the Internet to conduct electronic commerce. We target these
    constituencies through our direct sales force, business development teams
    and international sales offices.

  . Expand Alliances with Advertising Agencies. We intend to expand and
    strengthen our alliances with traditional advertising agencies to extend
    our direct sales efforts. We will continue to provide agencies with
    critical online media technology expertise, which we believe will
    accelerate our penetration of medium to large-sized corporate clients. We
    have already established alliances with agencies such as McCann-
    Erickson/A&L and Publicis & Hal Riney. We intend to pursue relationships
    with other advertising agencies by providing technology-enabled services
    and support for online advertising that can be fully integrated with
    their off-line initiatives.

  . Maintain Technology Differentiation. We believe that our technology is a
    key competitive differentiator. Our MOJO technology platform enables us
    to efficiently deploy services that give our clients innovative
    advertising capabilities while providing the ability to integrate their
    internal business information into their online messages in real time.
    Our Java objects-based architecture enables our services to scale
    geographically across the Internet and a large number of transactions and
    advertisers. We intend to extend our technology differentiation by
    incorporating additional functionality and services into our platform,
    such as the ability to execute transactions within the advertising
    message itself.

  . Enhance Sales Capabilities Through Marketing and Business
    Relationships. We plan to broaden our existing marketing and business
    relationships with companies such as DoubleClick, SAP Labs and Icon
    Medialab, and to build relationships with additional companies for our
    campaign and message management capabilities. We are seeking to work with
    traditional and interactive advertising agencies,

                                       36
<PAGE>


   online ad serving companies, ad publishing representatives, Web
   development and consulting firms, business application companies and
   systems integrators. Our objective is to establish alliances with these
   companies and accelerate our sales penetration into clients that would
   benefit from our services. In addition, we expect to develop and manage
   affiliate and sponsorship programs which generate shared revenues derived
   from prospective e-commerce-based services.

  . Deliver Flexible Online Marketing Solutions. We believe that online
    advertisers will increasingly demand greater flexibility and
    accountability in their advertising programs. Because we can unbundle our
    technology-enabled services, our services can be deployed together with
    the capabilities offered by other advertising and technology providers,
    such as DoubleClick. By working with third-party providers, we can offer
    specific services, such as dynamic tailored messaging, that complement
    their advertising services. This flexibility creates enhanced revenue
    opportunities and accelerates market adoption of our services and
    technology by targeting clients interested in unbundled elements of our
    services.

  . Broaden International Presence. We plan to expand our capabilities and
    presence internationally in order to capitalize on the global reach of
    the Internet. We also believe there is a significant opportunity to
    provide our services to companies based outside of the United States that
    require technology-enabled advertising services tailored for their local
    markets. We have recently opened a sales office in Hamburg, and by the
    middle of 2000, we expect to have established offices in London, Paris,
    Stockholm and Tokyo.

Our Services

  Our technology-based marketing services encompass campaign planning and
execution, online message management and campaign analysis. Our services can be
delivered individually or as a suite of services and are principally priced
based on cost per thousand impressions, cost per click, or cost per
acquisition, which can include sales and registrations.

  Our services can be offered as part of a complementary solution provided in
conjunction with services provided by other advertising and technology vendors.
In particular, our MOJO technology can be deployed with the ad serving
capabilities provided by other companies, such as DoubleClick, and interactive
ad agencies.
This allows us to work with clients of these service and technology providers
who do not wish to purchase all of our campaign management capabilities, but
still want to deploy our MOJO technology or any of our other services.

  The creative portion of our clients' advertisements are created by our
clients' advertising agencies, or internally by our clients' marketing staffs.
For example, we have worked with the ad agencies Publicis & Hal Riney and
McCann-Erickson/A&L to develop and implement advertising services for companies
such as Hewlett-Packard. If the ad agencies with which we currently work were
to develop technology that provides their clients with the same services that
our technology currently provides, our ability to generate revenues from the ad
agencies' clients could be harmed.

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<PAGE>

- --------------------------------------------------------------------------------
   Services                                 Description of Services
- --------------------------------------------------------------------------------

 Campaign Planning and Execution
                              . Develop an online media strategy based on
                                the client's business objectives and the
                                appropriate Internet media opportunities

                              . Plan and purchase media across Internet
                                advertising networks and independent Web
                                sites, employing various price structures

                              . Manage the electronic delivery of online
                                advertisements by serving the ads ourselves
                                or contracting with established third-party
                                ad-serving companies

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

 Message Management           . Apply targeting goals based on the specific
                                capabilities of each Web site or advertising
                                network considered for the marketing
                                campaign

                              . Adjust campaigns in real time across all Web
                                sites based on predetermined schedules or
                                the occurrence of defined events

                              . Customize messages in real time based on
                                customer profiling, changes in internal
                                business information, market events and
                                campaign performance as measured by standard
                                metrics or return on investment analysis

                              . Use Web browser-based tracking tools to re-
                                target consumers

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

 Campaign Analysis
                              . Track and monitor campaigns for results as
                                measured by Web site and advertisement

                              . Provide real-time reports customized by
                                performance data, including impressions,
                                click-throughs and conversions for each Web
                                site and advertisement

                              . Generate campaign return on investment
                                statistics summarizing results by categories
                                such as user-targeting data, inventory
                                changes, Internet sites and date/time

                              . Optimize campaigns based on ongoing
                                performance data

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

Campaign Planning and Execution

  . Campaign Planning. We develop Internet media strategies based on
    advertisers' business goals and advertising objectives, such as brand
    awareness, product trial and sales, and previous online performance, if
    available. We determine target audiences using demographic, geographic
    and consumer preference information, or consumers' areas of interest. Our
    online media programs can be developed independently or in conjunction
    with clients' off-line campaigns to deliver a consistent brand message at
    each point of contact.

  . Media Buying and Placement. We leverage our wholesale buying power in
    planning and buying across all advertising networks and independent Web
    sites. Each campaign is customized, incorporating sponsorships, keywords,
    run of site, specific position and remnant space, where applicable. Media
    purchases can be based on several models including cost per thousand
    impressions, cost per click, cost per acquisition and revenue-sharing
    programs. Our MOJO technology processes insertion orders systematically
    across networks and individual Web sites to deliver accurate ad
    placement.

  . Ad Serving. Our third-party ad serving capabilities allow adjustments to
    be managed quickly and efficiently because the only changes required to
    the advertisements are effected on our servers rather than on each
    individual Web site where the advertisements appear.


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<PAGE>


  . Message Re-targeting. We use Internet browser-based tracking tools to
    capture and analyze data on consumer behavior and site visitation
    patterns. We use this data to refine future messages to consumers whom we
    have previously identified. For example, we can track which product pages
    users visit, how far they proceed in the shopping process, and if they
    have made previous online purchases.

Message Management

  . Dynamic Messaging. We enable advertisers to modify advertising messages
    dynamically, that is, at any point in time. Online advertisements contain
    "data fields" where messages can change, such as products, prices or
    special offers. Message modification can be automated by establishing
    predefined events that determine message content, such as product
    rotations or price reductions. Advertisers can also make modifications
    manually, directly from their desktop computers.

  . Targeted Messaging Integrated with Business Data. Our messaging
    capabilities enable advertisers to use real-time business information,
    such as product availability and pricing, to deliver a customized message
    to each viewer. We assist advertisers with the development of business
    rules based on product database or business system information. During a
    campaign, our MOJO technology can make automatic modifications to the
    advertisements on the basis of these business rules. We believe that
    clients with time-sensitive inventory are particularly well-suited to
    take advantage of these capabilities. For example:

    . An airline promotes roundtrip fares between San Francisco and New
      York to business travelers. Fourteen days prior to the flight, the
      airline advertises seats at $956. The airline could specify that
      seven days before the flight, the price on the banner message would
      systematically change to $1,499. Based on excess seat availability
      two days prior to departure, the fare offered for a limited number of
      the seats would be automatically discounted to $799.

    . A hotel chain focuses its advertising campaign on reaching an 80%
      occupancy rate. When the occupancy rate of a particular hotel reaches
      this level, the message is automatically directed to promote another
      property within the chain.

  . Integration of Data From Third-party Vendors. In addition to customer
    profiling data that we compile, we have access to the extensive profiling
    data through our business and marketing alliance with DoubleClick. Our
    MOJO technology utilizes this data in creating, in real time, a
    customized message to be delivered to a consumer based on the consumer's
    profile, as well as the client's internal business data and market data.

  . Queued Creative. Advertising based on specific schedules or time-
    sensitive information can be pre-programmed across all campaign sites.
    For example, a banner for a promotion that starts and ends at an exact
    time or day can be queued to start and stop automatically at the
    appropriate times.

  . Storyboard Messaging. Using our technology, a "storyboard" of advertising
    messages can be constructed in a series. The campaign can be designed to
    show a set of advertisements in a predefined sequence for a particular
    consumer, regardless of which Web site in the campaign is viewed. This
    choreographs a series of customized messages based on the consumer's
    interests and online activity. For example, a viewer purchasing a
    computer online can be presented with advertisements for accessories the
    next time he or she accesses a Web site within the campaign.

  . Multiple Messaging. MOJO technology enables single advertisements to
    provide multiple click-through message options. The choice of message is
    determined by the location of the advertisement on which the consumer
    clicks. For example, if a consumer received a banner depicting a map of
    the United States and clicked on the state of California, the consumer
    would receive a different message than if he or she were to click on the
    state of Maryland.

Campaign Analysis

  . Campaign Tracking. We track performance statistics such as impressions,
    click-throughs and conversions, which include sales and other types of
    transaction activity such as registrations and requests for information,
    across all campaign sites. Activity is monitored by site, creative unit,
    such as a banner or side panel, and message content.

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<PAGE>


   Our technology enables tracking of performance metrics for standard
   advertisements and for the more difficult to monitor advertisements that
   incorporate audio and video components. We can also track advertising that
   is served by independent third-party ad servers.

  . Campaign Reporting. We provide a broad range of accurate and timely
    reporting capabilities customized to meet individual advertiser's needs.
    Clients are able to view secure, real-time campaign reports by
    performance statistics, including impressions, click-throughs, conversion
    rates and sales, at any time over the Internet in a summary format that
    provides results categorized by site and by advertisement.

  . Return on Investment Analysis. Return on investment reporting is
    customized to each advertiser and integrates sales and conversion data to
    generate campaign statistics in real time. Reports provide measurements
    on performance by tracking sales and other conversions criteria, such as
    registrations and information requests, as well as by tracking visitors
    who did not act immediately, but subsequently returned to the Web site
    and purchased.

  . Real-time Campaign Optimization. Our MOJO technology allows predefined
    business rules to automatically optimize campaigns. In addition, we can
    make real-time changes to campaigns based on ongoing performance data.
    Our customized, real-time reports facilitate quick determination of the
    effectiveness of sites and advertisements based on performance metrics,
    such as lowest cost per sale and highest sales volume.

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<PAGE>

Technology

Description of Our MOJO Technology Platform.

  Our proprietary MOJO technology platform utilizes a mobile Java object
architecture, each object being a discrete piece of software written in Java
code. These objects store critical information relevant to the execution of a
campaign, and can be controlled remotely, or through a computer not physically
located at the same place as the servers containing the advertisements. In
addition, these objects can exchange data with each other using the Java
language over our publish and subscribe-based messaging communication network.
"Publish and subscribe" is a communication method that allows the exchange of
information anonymously, which means that an advertiser's proprietary
information is not revealed or stored in the process. These objects are mobile
and platform-independent, meaning they can reside and be controlled on servers
operated by Mediaplex, the advertiser or any other third-party ad server using
different operating systems. We believe our MOJO technology facilitates timely,
efficient and accurate campaign execution and management as well as a secure
and efficient means of integrating a client's proprietary internal business
systems with the online advertising campaign. Our architecture is designed for
scalability and high performance to manage multiple advertising campaigns
across thousands of Web sites.

          [Graphic depiction of MOJO technology platform appears here]

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<PAGE>


  Mediaplex's MOJO architecture has three primary technical components:
advertising objects, network services and business integration:

    Advertising Objects. Advertising objects contain all information relevant
  to a campaign and manage the serving of each advertisement. Targeting rules
  residing in an ad-serving object determine, for example, the targeting
  profile upon which to focus and which message to send to a particular
  consumer. Tracking functions for an advertising campaign are also performed
  by these objects, which can be stored and executed on any server. The
  advertising objects may be modified or transferred in real time using
  computers physically located in the same facility and in facilities
  different from the servers on which the advertising objects are stored.

    Network Services. This component manages the entire campaign and
  coordinates communication between other objects and with our clients
  through our publish and subscribe messaging capability. This messaging
  capability receives events published or transmitted by various objects and
  forwards that information to other objects that are authorized to receive
  such information. This component contains the business rules for a campaign
  that determine, for example, which product information will be advertised
  and at what price, in response to changes in inventory levels. Reporting
  functions are also performed in this layer, which also provides access to
  relevant campaign data, through the publish and subscribe messaging
  capability. This network services layer applies predefined business rules
  to modify an advertising message on the basis of events summarized and
  stored within other objects within the network. This component is
  administered remotely, residing in our two co-location data centers, and
  communicates with the other technical components, namely, advertising
  objects and business integration, while executing the campaign.

    Business Integration. This component consists of objects that store the
  client's internal business data relevant to the campaign and generate
  events that are communicated to the network services layer and advertising
  objects. The underlying internal business information is not transferred
  and, thus, the integrity of a client's business information is protected
  and preserved under our architecture. In addition to communicating client
  events to the campaign, actual campaign results are communicated back to
  the client for analysis by the client and for updating the client's
  internal business data.

Competitive Advantages of Our Technology.

  We believe our technology provides these distinct competitive advantages:

  Real Time. Campaign customization and optimization occurs in or near real
time. Our MOJO technology is structured to enable our clients to establish
business rules which will automatically customize an advertising message in
response to predefined events the moment, or shortly after, the event occurs.
Real-time adjustments can also be made manually based on reports received
during ongoing campaigns.

  Flexibility. Our MOJO platform is designed to be flexible, supporting both
simple operations such as remote banner serving and click-through tracking and
more sophisticated operations, such as return on investment tracking and
automated feedback. Marketing campaigns can be modified in real time
automatically or manually, based on changes in the data stored in various
objects. These changes are communicated between objects through a continuous
communication loop facilitated by the publish and subscribe messaging
capabilities. Our architecture is also designed to be open and compatible with
most major business software applications and systems. Our MOJO technology is
easy to integrate and implement because it uses an industry standard language,
extensible mark-up language, commonly known as XML, for its data encoding and
communication. MOJO also supports major industry standards for programming
languages, operating systems and Internet protocols.

  Scability and Reliability. Our MOJO architecture is designed to scale in
anticipation of increased transaction demand and the ability of our systems to
process the transactions. Our technology is scalable by simply adding more
servers to accommodate system data traffic. The application logic of our
technology is designed to remain unchanged as the transaction volume grows. In
addition, our technology uses automatic failure protection combined with fault
tolerance, which allows campaign requests to be served even if one or more
servers are down.

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<PAGE>

Server Capacity Limitations.

  Based on our available servers and technology as of September 30, 1999, our
ad serving capacity was approximately 120 million impressions per day. At that
date, the highest number of impressions served on any particular day was
approximately 36 million. If we determine that our capacity will become
significantly constrained in the near future, we intend to increase the number
of servers and related technology to meet the additional capacity. In addition,
because of the significant fluctuations in the number of impressions served
from day to day, it is difficult to estimate the impact of a limitation on our
capacity. To date, capacity limitations have not been a problem for our ad
serving activities.

Resources Expended on Research and Development Activities.

  We have invested significant amounts toward research and development to date.
Our expenses in this area totaled approximately $347,000, $556,000 and $2.2
million in 1997, 1998 and the nine months ended September 30, 1999,
respectively.

Sales and Marketing

  We market and sell our services primarily through our field sales force,
which included 53 sales people as of September 30, 1999. Currently, we have
sales offices and support operations in San Francisco, New York City and
Hamburg, and plan to open additional sales offices in Western Europe and Tokyo
by mid-2000. We intend to broaden our global presence by expanding our
international sales force and by entering into marketing agreements with
international partners.

  Sales leads are primarily of two types: direct leads and leads from business
alliances. Direct leads are derived through field sales, client referrals, our
Web site, trade shows, and responses to our public relations and marketing
efforts. Business alliance leads are derived from companies that offer
complementary Internet services. These companies include traditional
advertising agencies, Web site design, Internet development and consulting
firms, business resource planning vendors, interactive ad agencies, system
integrators, and creative and software tool kit companies. Our sales account
teams typically include an account manager, associate account managers, a
campaign manager and an account coordinator.

  We use a variety of marketing programs to build awareness of Mediaplex and
its service offerings. These include collateral marketing materials, online and
off-line advertising, press coverage and other public relations efforts, direct
marketing, trade shows, seminars and conferences, relationships with recognized
industry analysts, and the Mediaplex Web site.

Business and Marketing Alliances

  An integral part of our strategy is to develop alliances and relationships
with complementary service providers to enhance our sales, marketing and client
development efforts in the United States, Europe and Asia. The alliances and
relationships that we have established to date are, except as described below,
non-exclusive and contain terms of six months to five years, some with renewal
options. We have established alliances within industries that we believe are
most appropriate for the propagation of our technology and services, as
follows:

  Internet Advertising. In August 1999, DoubleClick Inc., a provider of online
advertising services, and Mediaplex established an alliance to bridge the gap
between non-personally identifiable online target data and an advertiser's
business data. Through this relationship, we are able to integrate our MOJO
technology with DoubleClick's targeting system, known as DART, thereby enabling
creative messages in real time that are specifically targeted to a consumer
profile. Under our agreement with DoubleClick, we will coordinate our efforts
in DART-enabling the MOJO technology and jointly marketing our services to
prospective clients. The relationship also allows us to use the DART system,
where appropriate, and reduce our own serving costs as we manage an increasing
number of advertisements. We are required to pay DoubleClick a fee for
advertisements served by DoubleClick under this agreement; however, no fees
have been paid to DoubleClick as of September 30, 1999.

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<PAGE>


  Enterprise Resource Planning. In August 1999, we entered into an agreement
with SAP Labs, Inc., a subsidiary of SAP AG, an enterprise resource planning,
or ERP, software company. Under the terms of our agreement, we will create an
interface to SAP's R3 ERP system that will enable SAP's enterprise customers to
implement our MOJO technology in their e-commerce marketing programs.

  Operating Resource Management. In September 1999, Mediaplex and Ariba, Inc.
entered into a non-binding memorandum of understanding to integrate our real-
time online media buying technology into the Ariba Network. Ariba provides an
Internet-based system that enables companies to automate their online
procurement of goods and services. The Mediaplex and Ariba integrated service
is expected to enhance the efficiency of managing online advertising campaigns
for the Ariba Network customers by providing an automated system for the
transmittal and acknowledgement of advertisement insertion and change orders
using adXML, our version of XML. In addition, we are co-sponsoring a Web site
and are working together to make adXML an open standard, accessible to all
advertisers and advertising agencies.

  System Integration. In September 1999, Mediaplex entered into an agreement
with OTP Software, Inc., a systems integrator specializing in Oracle and IBM
software. OTP Software will provide interfaces for MOJO technology into Oracle
and IBM applications.

  Internet Development and Consulting. In July 1999, we entered into a
preferred provider agreement with Icon Medialab, a global Internet architect
for companies integrating Internet-based technology with business strategies.
Icon Medialab's services include strategy consulting, system integration,
interface design and usability testing for enhanced customer relations. Under
our agreement with Icon Medialab, we will cross-refer clients and collaborate
on joint marketing and strategic consumer development programs. We also believe
that we will benefit from Icon Medialab's presence and marketing capabilities
in Europe.

  Cable Television Providers. In August 1999, Mediaplex and Across Media
Networks entered into an agreement to offer marketers the capability to match a
specific consumer with a specific offer, both on cable television and the
Internet, driven by business rules and relevant marketing data. Across Media
Networks designs and operates private label cable channels to enable cable
operators to outsource the creation of branded, advertiser-supported subscriber
information channels, and serves over three million subscribers in more than
75 cities nationwide. We will provide MOJO technology to Across Media Networks
exclusively in conjunction with online marketing and advertising programs for
its CityHits Internet business and clients.

  International Alliances. In April 1999, Zeron Capital Ltd., a Japanese
merchant bank, investment management and venture capital firm, invested $2.0
million in our company, and in June 1999, invested an additional $3 million.
Zeron Capital Ltd. has agreed to use its best efforts to help secure our
presence in Japan, establish alliances with major companies in Japan and
develop an international presence in Asia. We believe that the Japanese market
represents significant growth opportunities for us and will allow us to expand
in other Asian markets. We are currently in discussions with Zeron Capital,
Ltd. to establish a joint venture to develop Japanese leads for our MOJO
technology and our campaign management services.

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<PAGE>

Our Clients

  As of September 30, 1999, Mediaplex had over 50 active clients. The following
is a list of all of our clients that purchased more than $50,000 in services
from January 1, 1999 to September 30, 1999:

                                 Direct Clients

<TABLE>
         <S>                                        <C>
         AnyDay.com                                 LuckySurf.com
         Ashford.com                                MacMall/Creative Computers
         Buy Software                               musicmaker.com
         Capstone Studio                            Mama Systems, Inc.
         Cassara Enterprises Ltd.                   MyShopNow.com
         DATEK Online                               myTrack.com
         DriveSavers                                OfficeMax.com
         Dynamind                                   PC Flowers & Gifts, Inc.
         eCOST.com                                  PCMall/Creative Computers
         eFax.com                                   Providian Financial
         eVite.com                                  School Specialty
         Financial Engines, Inc.                    ShopNow.com
         Flower Farm                                Strong Funds
         FreeShop.com                               ToyTime.com
         Fresh Flower Source                        uBid
         Global Admin UK Ltd.                       Virtumundo, Inc.
         Investor's Business Daily                  Youbet.com
         Kelltech                                   1800DAYTRADE.com
</TABLE>

                              Advertising Agencies

               .  McCann-Erickson/A&L for Silicon Graphics, Inc. and Siebel
                  Systems
               .  Publicis & Hal Riney for Sprint PCS and Hewlett-Packard

  In 1998, DATEK Online and uBid accounted for approximately 56% and 21% of our
revenues, respectively. In the first nine months of 1999, DATEK Online,
ShopNow.com and Publicis & Hal Riney accounted for approximately 17%, 11% and
10% of our revenues, respectively.

Client Case Studies

Tickets.com

  Headquartered in Costa Mesa, California, Tickets.com provides fully
integrated automated ticketing and information solutions over the Internet for
the performing arts, professional sports, general admission and live
entertainment markets. Tickets.com also manages a live ticket auction service
for person-to-person transactions.

 .  Challenge: Tickets.com's previous online marketing campaign was not targeted
   to a Web site visitor's music concert genre preference or geographical
   location, nor did it take into account real-time ticket inventory levels.
   Tickets.com wanted to test a targeted online advertising program that could
   leverage its database information by linking a potential customer's profile
   (e.g., music preference and geographic location) with appropriate auction
   concert-ticket inventory in real time.

 .  Mediaplex Solution: Mediaplex designed and implemented a controlled
   advertising test that, using MOJO technology, delivered real-time, targeted
   banner advertisements to the Audiofind.com site based on visitor profiles
   and Tickets.com auction inventory levels. For example, a Web site visitor
   from California

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<PAGE>

   accessing the Country Music Web page on Audiofind.com would be served a
   banner for an upcoming country music concert in Los Angeles. The banner
   incorporated various information from the Tickets.com database including the
   artist's name or name of event, number of tickets available, date, venue,
   city, state and price, and enabled visitors to click through to the auction
   page. For the test, 30 separate banners promoted individual concerts across
   various genres. In addition, a default Tickets.com banner was used as a
   control, or baseline measurement, on the Audiofind.com home page and on
   genre-specific Web pages with no corresponding auction.

 .  Result: At the end of the initial nine-day test period, the targeted auction
   banner click-through rate from Audiofind.com banners had reached 0.54%, a
   440% increase over the 0.10% default Tickets.com banner click-through rate.
   Tickets.com and Mediaplex are currently planning the next phase of the
   market test with a larger media buy across multiple geographic areas.

Publicis & Hal Riney for Hewlett-Packard

  Mediaplex worked with Publicis & Hal Riney to develop an online marketing
program for Hewlett-Packard, one of the world's largest computer companies
producing more than 29,000 products for personal use and use in industry,
business, engineering, science, medicine and education.

 .  Challenge: Hewlett-Packard required an online marketing program that
   entailed extensive tracking, reporting and analysis for four separate
   products as it began to market its full line of business PCs and servers
   over the Internet.

 .  Mediaplex Solution: Mediaplex developed and managed an online advertising
   campaign for Hewlett-Packard's laptop, business PC, server and high-end work
   station products. Working closely with Hewlett-Packard and Publicis &
   Hal Riney, Mediaplex developed four strategic media plans to reach targeted
   audiences based on each product's specific user profile. The Web pages that
   housed the product information resided on Mediaplex servers, which enabled
   Mediaplex to accurately track both the time spent viewing product
   information, and the viewer's next step. Mediaplex provided a comprehensive
   analysis of customized metrics reflecting the results of the campaigns as
   they progressed, including numbers of impressions and click-through rates
   achieved for each banner.

 .  Results: Using MOJO technology, Mediaplex modified advertisements and
   placements, in real time, based on a continuous analysis of the campaign's
   performance. By tracking movements made on each product page, Mediaplex was
   able to determine for Hewlett-Packard, on a product by product basis,
   whether consumers were clicking through to gather information, make a
   purchase, reach a sales representative or were merely browsing. The viewer
   behavior information collected during the campaign is currently being
   analyzed for future online programs.


Technical Support

  We provide extensive technical strategy and support throughout the
implementation and maintenance phases of the deployment of our services. This
support is comprised of three key components: Network Operations, Technical
Account Coordination and MOJO Implementation.

Network Operations

  Our network operations organization is responsible for ensuring that our
network and servers are fault-tolerant. We have organized our network of
servers to provide significant protection against potential breakdown or
outages.

Technical Account Coordination

  We believe that our technical account procedures protect the client from data
loss. Each account team, comprised of a customer support manager, software
engineer and director of systems operations, holds frequent meetings to discuss
each ad campaign currently being conducted. These teams review each client's
campaign for which the team is responsible to ensure the client's program is
operating trouble-free.

                                       46
<PAGE>

  Our account coordinators also work with each publisher to provide smooth
technical implementation of the campaign, and test each technical aspect of the
campaign before it is launched.

MOJO Implementation

  Our engineering organization takes an in-depth and focused approach to the
implementation of our MOJO technology for each client's online campaign. Each
team meets with its clients to fully understand the client's environment, its
computer systems and exactly how the MOJO technology needs to work with the
client's specific computer systems. The team also works with the client to
define the campaign needs and then implements an appropriate plan based on the
campaign goals set by the client. Once MOJO is installed, the team performs
ongoing implementation and support of the client's campaign.

Privacy of Client Data

  The effectiveness of our services and technology relies on the effectiveness
of techniques for profiling Internet users, which may raise privacy concerns.
Our clients generally have implemented security features to protect the privacy
and integrity of the data collected from their users. However, this information
may be susceptible to hacker interception, break-ins and disruption. In
addition, we do not aggregate, share or sell any data we receive on profiling
efforts.

  We face privacy issues related to our ability to access our clients' internal
business information data. In some cases, our clients have expressed concern
that, because we manage advertising campaigns for them as well as for their
competitors, their confidential business information may be exposed to these
competitors. In order to prevent the unintentional exposure of confidential
business information of our clients, we have created safeguards for their data,
including the use of separate secure servers for clients with any potential
product overlap, independent client teams with no overlapping personnel, and
confidentiality agreements on behalf of the advertising agencies with which we
work and on behalf of the client. In addition, we maintain a strict policy that
no client data should be shared, sold or aggregated with any other client's
data.

Intellectual Property

  To protect our proprietary rights, we rely generally on patent, copyright,
trademark and trade secret laws, and confidentiality agreements or licenses
with employees, consultants, vendors, clients and corporate parties. Despite
these protections, a third party could, without authorization, disclose, copy
or otherwise obtain and use our technology or develop similar technology
independently.

  We currently have one patent pending in the United States relating to our
MOJO architecture. We cannot assure you that our pending, or any future, patent
application will be granted, that any existing or future patent will not be
challenged, invalidated or circumvented, or that the rights granted under or
any patent that may issue will provide competitive advantages to us. Many of
our current and potential competitors dedicate substantially greater resources
to the protection and enforcement of intellectual property rights, especially
patents. If a blocking patent has issued or issues in the future to a
third party, we would need either to obtain a license to, or to design around,
that patent. We may not be able to obtain a license on acceptable terms, if at
all, or design around the patent, which could harm our ability to provide our
services.

  We pursue the registration of our trademarks and service marks in the U.S.
and in other countries, although we have not secured registration of all of our
marks. As of September 30, 1999, we had no registered U.S. trademarks or
service marks; however, we have applied for registration of our Mediaplex and
MOJO trademarks, which we believe are key to identifying and differentiating
our services from those of our competitors. In addition, the laws of some
foreign countries will not protect our proprietary rights to the same extent as
do the laws of the U.S., and effective patent, copyright, trademark and trade
secret protection may not be available in these jurisdictions.

  We may, in the future, license our proprietary rights, in particular our MOJO
technology, to third parties. These licensees may fail to abide by compliance
and quality control guidelines with respect to our proprietary rights or take
actions that would severely harm our ability to use our proprietary rights and
our business.

                                       47
<PAGE>

  We attempt to avoid infringing known proprietary rights of third parties in
our product development efforts. We have conducted an independent patent search
for prior art related to our MOJO architecture. This patent search did not
uncover any references that would anticipate our patent claim; however, this
patent search was not exhaustive and may not have uncovered all prior art
applicable to our MOJO architecture. In addition, it is difficult to proceed
with certainty in a rapidly evolving technological environment in which there
exist numerous patent applications pending, many of which are confidential when
filed, with regard to similar technologies. If we were to discover that our
technology violates third-party proprietary rights, we might not be able to
obtain licenses or continue offering our services based on our technology
without substantial reengineering. Any efforts to undertake this reengineering
might not be successful, and any necessary licenses might not be available on
commercially reasonable terms, if at all.

  Litigation for claims of infringement might not be avoided or settled without
incurring substantial expenses and damage awards. In addition, any of these
claims, even if not meritorious, could result in the expenditure of significant
financial and managerial resources and could result in injunctions preventing
us from delivering our services based on our technology or licensing our
technology to third parties or clients. These claims could harm our business.

  In the future, we may license technology that will be integrated with our
internally developed software and used in our services. We cannot assure you
that third-party technology licenses will become or will continue to be
available to us on commercially reasonable terms. The loss of any of these
technologies could harm our business. In addition, by licensing technology from
third parties, we may become susceptible to claims for infringement with
respect to this third-party technology. Even if we receive broad
indemnification from our licensors, third-party indemnitors are not always well
capitalized and may not be able to indemnify us in the event of infringement,
resulting in substantial exposure to us. Any infringement claims, even if not
meritorious, could result in the expenditure of significant financial and
managerial resources in addition to potential product redevelopment costs and
delays, all of which could harm our business.

Competition

  The Internet media services market, which includes planning media campaigns,
buying advertising space, ad serving and tracking and reporting results of
advertising, is extremely competitive and likely to become more intense due to
the lack of significant barriers to entry. In particular, advertising agencies
without in-house online media management capabilities, including those with
which we currently work, may develop these capabilities in the future. We
believe that, in addition, competition will continue to increase as a result of
industry mergers, partnerships and consolidation. For example, AdForce and
Flycast have recently been acquired by CMGI, AdKnowledge has recently been
acquired by Engage Technologies, a subsidiary of CMGI, and NetGravity has
recently been acquired by DoubleClick. As we expand internationally, we expect
to face competition from internationally based competitors, such as Mindshare
Digital and Publicis Technology, as well as our domestic competitors with
international operations, such as BBDO Interactive, Leo Burnett and the
Interpublic Group. Many of our existing competitors, as well as a number of
potential new competitors, have longer operating histories, greater name
recognition, larger client bases and significantly greater financial, technical
and marketing resources than we have. The following categories represent
current and potential competition:

  . online media planning and buying services, such as Avenue A;

  . ad serving companies, such as AdForce, DoubleClick and Engage
    Technologies;

  . publisher networks that provide services directly to clients, such as
    Flycast Communications and 24/7 Media;

                                       48
<PAGE>

  . organizations that manage affiliate programs, such as LinkShare; and

  . advertising agencies that have or elect to develop in-house online media
    management capabilities, such as Lowe Interactive.

  We believe that our ability to compete depends upon many factors both within
and outside of our control, including:

  . effectiveness, ease of use, performance and features of our technology;

  . client perceptions of the effectiveness of our services and technology;

  . the price of our services;

  . our ability to service our clients effectively over a broad geographic
    basis; and

  . the timing and acceptance of new services and enhancements to existing
    services developed by us or our competitors.

Employees

  As of September 30, 1999, we had 109 full-time employees. Of these employees,
36 were engaged in research and development, 53 were engaged in sales and
marketing and 20 were engaged in finance and administration. None of our
employees is represented by a labor union or a collective bargaining agreement.
We have not experienced any work stoppages and consider our relations with our
employees to be good.

Facilities

  We currently lease approximately 22,100 square feet of office space for our
headquarters in two buildings, located in San Francisco, California. In
November 1999, we expect to move into a new location for our headquarters in
San Francisco. We also lease approximately 13,200 square feet of a facility in
San Jose, California that houses our research and development organization and
approximately 7,700 square feet in New York City for a sales office. In
addition, we use two third-party, fully redundant co-location facilities that
house our Web servers in San Francisco and San Jose, California and we are
currently seeking to obtain additional co-location facilities in other areas in
the United States. We cannot assure you that we will be able to locate and
lease additional acceptable co-location space at a reasonable price.

Legal Proceedings

  From time to time, we may become involved in litigation relating to claims
arising from the ordinary course of our business. We believe that there are no
claims or actions pending or threatened against us, the ultimate disposition of
which would have a material adverse effect on us.

                                       49
<PAGE>

                                   MANAGEMENT

Directors and Executive Officers

  The following table sets forth certain information with respect to our
directors and executive officers as of September 30, 1999:

<TABLE>
<CAPTION>
              Name             Age                   Position
   --------------------------- --- --------------------------------------------
   <C>                         <C> <S>
   Gregory R. Raifman.........  40 Chairman of the Board of Directors and Chief
                                   Executive Officer

   Jon L. Edwards.............  39 President and Director

   Walter Haefeker............  38 Chief Operating Officer

   Ruiqing "Barclay" Jiang....  37 Chief Technology Officer

   Timothy M. Favia...........  37 Executive Vice President, Sales and
                                   Development

   Sandra L. Abbott...........  52 Senior Vice President, Chief Financial
                                   Officer and Secretary

   Robert M. Henely...........  47 Senior Vice President, Technical Operations

   M. Joy Fauvre..............  48 Senior Vice President, Marketing

   Alan M. Raifman............  45 Vice President, Business and Legal Affairs

   James DeSorrento ..........  56 Director

   Lawrence D. Lenihan, Jr. ..  34 Director

   Peter S. Sealey ...........  59 Director

   A. Brooke Seawell .........  51 Director
</TABLE>

  Gregory R. Raifman has served as our Chairman of the Board of Directors and
Chief Executive Officer since September 1998, and Chief Executive Officer and
sole director of MediaPlex, Inc., our former wholly-owned subsidiary since
April 1998. Since August 1993, Mr. Raifman has also served as a general partner
of Raifman & Edwards LLP, a law firm. Since September 1994, Mr. Raifman has
also served as a managing member of PointBreak Ventures, LLC, a venture capital
firm. Mr. Raifman received an A.B. in economics and history from the University
of Michigan and a J.D. from Georgetown University Law Center.

  Jon L. Edwards has served as our President and a member of our board of
directors since April 1998. Since August 1993, Mr. Edwards has also served as a
general partner of Raifman & Edwards LLP. Since September 1994, Mr. Edwards has
also served as a managing member of PointBreak Ventures, LLC. Mr. Edwards
received an A.B. in engineering science from Dartmouth College and a J.D. from
Georgetown University Law Center.

  Walter Haefeker has served as our Chief Operating Officer since September
1998. Since September 1994, Mr. Haefeker has served as a managing member for
PointBreak Ventures, LLC. From March 1994 to April 1995, Mr. Haefeker served as
chairman of the board of directors for CADIS Software, Ltd., a software
company. Mr. Haefeker received an Abitur in chemistry and physics from Theodor-
Heass Gymnasium, Pinneberg, Germany.

  Ruiqing "Barclay" Jiang has served as our Chief Technology Officer since
March 1999. Prior to joining Mediaplex, Mr. Jiang served as president of
Netranscend Software, Inc., a business software company, from November 1996
until it was acquired by Mediaplex in March 1999. From October 1993 to
September 1997, Mr. Jiang served as an engineering manager for FutureLabs,
Inc., a software company. Mr. Jiang received a B.S. in computer science from
Xi'an Jiaotong University, China and an M.S. in applied statistics from
Louisiana State University.

  Timothy M. Favia has served as our Executive Vice President, Sales and
Development since January 1999. Prior to joining Mediaplex, Mr. Favia was a co-
founder of Oxygen Electronics, LLC, a distributor of electronic components,
where he served as managing partner from June 1997 to December 1998. From
January 1996 to May 1997, Mr. Favia served as vice president, western region,
of Open Port Technology, an Internet messaging

                                       50
<PAGE>

services company. From July 1988 to January 1996, he served as director of
international sales for Thomson Software Products, a software company. Mr.
Favia received a B.A. in political science from Fairfield University.

  Sandra L. Abbott has served as a Senior Vice President and our Chief
Financial Officer and Secretary since August 1999. Prior to joining Mediaplex,
Ms. Abbott served as chief financial officer for 8x8, Inc., a manufacturer of
digital telecommunication products, from June 1995 to August 1999. From April
1991 to June 1995, Ms. Abbott served as controller for 8x8, Inc. Ms. Abbott
received a B.A. in political science from the University of California,
Riverside and an M.B.A. from Santa Clara University.

  Robert M. Henely has served as our Senior Vice President, Technical
Operations since March 1999. Prior to joining Mediaplex, Mr. Henely served as
director of engineering for Boole & Babbage, Inc., a software company, from
December 1997 to March 1999. From November 1981 to December 1997, Mr. Henely
served as a research and development manager at Hewlett-Packard Company.
Mr. Henely received a B.S. in economics from California State University, Chico
and an M.S. in econometrics from the University of California, San Diego.

  M. Joy Fauvre has served as our Senior Vice President, Marketing since July
1999. Prior to joining Mediaplex, Ms. Fauvre served as a marketing director for
Heller Financial, a commercial lender, from October 1994 to July 1999. From
June 1994 to October 1994, Ms. Fauvre served as acting advertising manager for
Qantas Airways, a commercial airline, and from August 1991 to January 1994, she
served as an account supervisor for D'Arcy Masius Benton & Bowles, an
advertising agency. Ms. Fauvre received a B.A. in theatre from the University
of California, Santa Barbara and an M.A. in theatre from Ball State University.

  Alan M. Raifman has served as our Vice President, Business and Legal Affairs
since October 1998. Prior to joining Mediaplex, Mr. Raifman served as an
associate for Albert A. Rettig & Associates, a business services company, from
June 1997 through January 1999. From July 1989 to June 1997, Mr. Raifman served
as President and a director of Little Cargo, Inc., a juvenile product
development company that he co-founded. Mr. Raifman is currently on the board
of directors of Little Cargo, Inc. Mr. Raifman received a B.A. in history and a
J.D. from Washington University.

  James DeSorrento has served as a member of our board of directors since
August 1999. Since June 1982, Mr. DeSorrento has served as chief executive
officer and chairman of the board of Triax Telecommunications Company, LLC and
its predecessor, Triax Communications Corporation, a cable television operating
company. Mr. DeSorrento received a B.A. in English from St. Michael's College.

  Lawrence D. Lenihan, Jr. has served as a member of our board of directors
since August 1999. Since January 1999, Mr. Lenihan has served as fund manager
for Pequot Capital Management, Inc., a venture capital firm. From October 1996
to December 1998, Mr. Lenihan served as fund manager for Dawson-Sanberg Capital
Management, a venture capital firm. From August 1993 to October 1996, Mr.
Lenihan served as a principal for Broadview Associates, an investment bank. Mr.
Lenihan also serves as a member of the boards of directors of Digital
Generation Systems, Inc., a provider of distribution services for ad agencies
and broadcasters, STM Wireless, Inc., a satellite and wireless-based
communications company, and Triken Technologies, Inc., a semiconductor-
processing equipment company, as well as several private companies. Mr. Lenihan
received a B.S.E.E. in electrical engineering from Duke University and an
M.B.A. from the Wharton School of Business at the University of Pennsylvania.

  Peter S. Sealey has served as a member of our board of directors since August
1999. Since September 1994, Dr. Sealey has served as an adjunct professor of
marketing at the Haas School of Business at the University of California,
Berkeley where he also has served as a co-director of the Center for Marketing
and Technology. Prior to that, Dr. Sealey was employed by the Coca Cola Company
for 24 years, where he held a series of senior management positions, including
senior vice president, global marketing. Dr. Sealey serves as a member of the
boards of directors of US Web/CKS, an Internet professional services firm,
Autoweb.com Inc., a consumer automotive Internet site, bamboo.com, a producer
of virtual tours for the real estate industry on the

                                       51
<PAGE>

Internet, and Cybergold, Inc., an Internet-based direct marketing and
advertising company, as well as several private companies. Dr. Sealey received
a B.S.B.A. in business from the University of Florida, an M.I.A. in industrial
administration from Yale University, and an M.A. in management and Ph.D. in
management and information technology from the Peter F. Drucker Graduate
Management Center at The Claremont Graduate University.

  A. Brooke Seawell has served as a member of our board of directors since
August 1999. From January 1997 to August 1998, Mr. Seawell served as the
executive vice president of NetDynamics Inc., a business network applications
server software company. From March 1991 to January 1997, Mr. Seawell served as
the senior vice president of finance and operations of Synopsys Inc., an
electronic design automation company. Mr. Seawell serves as a member of the
boards of directors of NVIDIA Corporation, a three-dimensional graphics
processor, Informatica Corporation, a data integration software company, and
Accrue Software, Inc., an internet data collection and analysis software
company, as well as several private companies. Mr. Seawell received a B.A. in
economics and an M.B.A. in finance from Stanford University.

Board of Directors

  Our board of directors is currently comprised of six directors. Our restated
certificate of incorporation, to be filed upon the closing of this offering,
states that the board of directors will be divided into three classes as nearly
equal in size as possible with staggered, three-year terms. The term of office
of our Class I directors will expire at the annual meeting of stockholders to
be held in 2000; the term of office of our Class II directors will expire at
the annual meeting of stockholders to be held in 2001; and the term of office
of our Class III directors will expire at the annual meeting of the
stockholders to be held in 2002. Messrs. Lenihan and Sealey have been
designated as Class I directors; Messrs. Edwards and DeSorrento have been
designated as Class II directors; and Messrs. Raifman and Seawell have been
designated as Class III directors. At each annual meeting of the stockholders
after the initial classification, the successors to the directors whose terms
have expired will be elected to serve from the time of election and
qualification until the third annual meeting following their election or until
their successors have been duly elected and qualified, or until their earlier
resignation or removal, if any. In addition, our bylaws, to be adopted upon the
closing of this offering, provide that the authorized number of directors may
be changed by resolution of the board of directors. Any additional
directorships resulting from an increase in the number of directors will be
distributed among the three classes so that, as nearly as possible, each class
will consist of one-third of the total number of directors. The classification
of our board of directors could have the effect of making it more difficult for
a third party to acquire, or of discouraging a third party from acquiring,
control of Mediaplex. See "Description of Capital Stock."

  Each officer is elected by, and serves at the discretion of, the board of
directors or until his or her successor has been duly elected and qualified.
Each of our executive officers and directors, other than non-employee
directors, devotes his or her full time to our affairs. Our non-employee
directors devote the amount of time necessary to discharge their duties to us.
Gregory R. Raifman, our Chairman of the Board of Directors and Chief Executive
Officer is the brother of Alan M. Raifman, our Vice President, Business and
Legal Affairs. There are otherwise no family relationships among any of our
directors, officers or key employees.

Board Committees

  The board of directors has established an audit committee to meet with and
consider suggestions from members of management and our internal accounting
personnel, as well as our independent accountants, concerning our financial
operations. The audit committee also has the responsibility to review our
audited financial statements and consider and recommend the employment of, and
approve the fee arrangements with, independent accountants for both audit
functions and for advisory and other consulting services. The audit committee
is currently comprised of Messrs. DeSorrento and Seawell.

  The board of directors has also established a compensation committee to
review and approve the compensation and benefits for our key executive
officers, administer our equity incentive plans and make

                                       52
<PAGE>

recommendations to the board of directors regarding such matters. The
compensation committee is currently comprised of Messrs. Lenihan and Sealey.

Compensation Committee Interlocks and Insider Participation

  Prior to establishing the compensation committee, the board of directors as a
whole performed the functions delegated to the compensation committee. No
member of the board of directors or the compensation committee serves as a
member of the board of directors or compensation committee of any entity that
has one or more executive officers serving as a member of our board of
directors or compensation committee.

Director Compensation

  Directors do not currently receive any cash compensation from us for their
service as members of the board of directors; however, directors are reimbursed
for all reasonable expenses incurred by them in attending board and committee
meetings. Employee and non-employee directors are also eligible to receive
options under our 1999 Stock Plan and employee directors are eligible to
participate in our 1999 Employee Stock Purchase Plan. In August 1999, Messrs.
DeSorrento and Seawell and Dr. Sealey were each granted an option to acquire
50,000 shares of common stock at an exercise price of $3.25 per share upon
their appointment to our board of directors. The options vest over a four year
period but may be exercised at any time. See "--Equity Incentive Plans."

Executive Compensation

  The following table sets forth the total compensation received for services
rendered to us during 1998 by our Chief Executive Officer and two of our other
executive officers. Except as set forth below, no other employee received
salary and bonus in 1998 in excess of $100,000. These three officers are
referred to as the named executive officers in this prospectus. In 1998,
Messrs. Gregory Raifman and Jon Edwards, general partners of Raifman & Edwards,
LLP, provided legal and management services to us, for which Raifman & Edwards,
LLP was paid approximately $197,000. See "Related Party Transactions." Except
as disclosed below and in "Related Party Transactions," we gave no bonuses,
stock-based compensation or other compensation to our named executive officers
in 1998.

                           Summary Compensation Table

<TABLE>
<CAPTION>
                                                             Annual Compensation
                                                             -------------------
Name and Principal Position                                      Salary ($)
- ------------------------------------------------------------ -------------------
<S>                                                          <C>
Gregory R. Raifman, Chief Executive Officer (1).............      $180,000

Jon L. Edwards, President (2)...............................       180,000

Walter Haefeker, Chief Operating Officer (3)................       150,000
</TABLE>
- --------
(1) The salary amount represents the amount Mr. Raifman would have earned if he
    had been employed by us for the entire year. Mr. Raifman's actual salary
    earned was $35,000.

(2) The salary amount represents the amount Mr. Edwards would have earned if he
    had been employed by us for the entire year. Mr. Edward's actual salary
    earned was $35,000.

(3) The salary amount represents the amount Mr. Haefeker would have earned if
    he had been employed by us for the entire year. Mr. Haefeker's actual
    salary earned in 1998 was $41,100.

  The 1999 annual base salary rates for Messrs. Raifman, Edwards and Haefeker
are $250,000, $250,000 and $225,000, respectively. In addition, we hired the
following executive officers in 1999 at the following annual salaries: Ruiqing
"Barclay" Jiang, $180,000; Timothy M. Favia, $175,000; Sandra L. Abbott,
$170,000; Robert Henely, $150,000; M. Joy Fauvre, $140,000; and Alan M.
Raifman, $90,000.


                                       53
<PAGE>

Option Grants and Exercises in Last Fiscal Year and Fiscal Year End Option
Values

  No named executive officers were granted or held any options to purchase our
common stock at any time in 1998. In February 1999, however, Gregory R.
Raifman, Jon L. Edwards and Walter Haefeker were granted options under our 1999
Stock Plan to purchase 1,750,000, 1,500,000 and 1,250,000 shares of common
stock, respectively, at a purchase price of $0.50 per share, of which 388,889
shares, 333,333 shares and no shares, respectively, had vested as of December
31, 1998. None of these options has been exercised to date.

Employment Agreements

  In connection with our hiring and retention of each of Gregory R. Raifman,
Jon L. Edwards and Walter Haefeker, we entered into employment agreements, each
dated February 19, 1999, in which we agreed to pay each of them a specified
base salary and grant each of them options to purchase our common stock, and
each executive officer agreed to enter into a three-year employment term with
us. Upon the expiration of the three-year term, employment with us becomes
terminable at will. All options vest at the rate of 1/6th of the shares on the
six-month anniversary of the vesting commencement date, and 1/36th of the
shares per month thereafter as long as the optionee is employed by us. The
following table sets forth the stock options granted to each executive officer
under his employment agreement with us:

<TABLE>
<CAPTION>
                                                                  Exercise Price
Name                                              Options Granted    Per Share
- ------------------------------------------------- --------------- --------------
<S>                                               <C>             <C>
Gregory R. Raifman...............................    1,750,000        $0.50

Jon L. Edwards...................................    1,500,000         0.50

Walter Haefeker..................................    1,250,000         0.50
</TABLE>

  Under the terms of each employment agreement, if we terminate employment with
the executive officer without cause, we are required to pay him severance
payments of 1/13th of his base salary for each complete month previously
worked; however, the aggregate severance payments are not to exceed his annual
base salary. Additionally, each executive officer has agreed to not compete
with us or not solicit others from us for a period of one year following his
termination with us.

Equity Incentive Plans

  1997 Stock Plan. Our 1997 Stock Plan provides for the granting to employees
of incentive stock options within the meaning of Section 422 of the Internal
Revenue Code of 1986, as amended, and for the granting to employees and
consultants of nonstatutory stock options and stock purchase rights. As of
September 30, 1999, options to purchase 243,000 shares of common stock were
outstanding under our 1997 Stock Plan. Our board of directors has determined
that no further options will be granted under the 1997 Stock Plan after this
offering. The 1997 Stock Plan provides that, if we merge with or into another
corporation or sell substantially all of our assets, each outstanding option
must be assumed or substituted for by the successor corporation. If the
successor corporation refuses to assume or substitute for the Mediaplex
options, the Mediaplex options will terminate as of the closing of the merger
or sale of assets.

  Amended and Restated 1999 Stock Plan. Our 1999 Stock Plan was initially
adopted by our board of directors and shareholders in February 1999. It was
amended and restated by our board of directors in August 1999, and by our
stockholders in September 1999. The Amended and Restated 1999 Stock Plan will
become effective upon the closing of this offering.

  The Amended and Restated 1999 Stock Plan provides for the grant of incentive
stock options to employees, including officers and employee directors, and for
the grant of nonstatutory stock options and stock purchase rights to employees,
directors and consultants.

                                       54
<PAGE>

  We have reserved 12,000,000 shares of our common stock for issuance pursuant
to the Amended and Restated 1999 Stock Plan. In addition, commencing January 1,
2000, the number of shares reserved for issuance under the Amended and Restated
1999 Stock Plan will be increased by an amount equal to the least of (a)
1,000,000 shares, (b) 4% of the outstanding shares or (c) an amount determined
by our board of directors.

  Unless terminated sooner, the Amended and Restated 1999 Stock Plan will
automatically terminate ten years from the effective date of this offering.

  The administrator of our stock plan has the power to determine:

  . the terms of the options or stock purchase rights granted, including the
    exercise prices of the options or stock purchase rights;

  . the number of shares subject to each option or stock purchase right;

  . the exercisability of each option or stock purchase right; and

  . the form of consideration payable upon the exercise of each option or
    stock purchase right.

  In addition, the administrator has the authority to amend, suspend or
terminate the stock plan, so long as this action does not affect any shares of
common stock previously issued and sold or any option previously granted under
the Amended and Restated 1999 Stock Plan. The maximum number of shares covered
by an option that each optionee may be granted during a fiscal year is 500,000
shares. In addition, in connection with an optionee's initial employment with
us, the optionee may be granted an option covering an additional
500,000 shares.

  Options and stock purchase rights granted under our Amended and Restated 1999
Stock Plan are generally not transferable by the optionee, and each option and
stock purchase right is exercisable during the lifetime of the optionee only by
the optionee. Options granted under the Amended and Restated 1999 Stock Plan
must generally be exercised within three months after the end of the optionee's
status as an employee, director or consultant of Mediaplex, or within 12 months
after the optionee's termination by death or disability, but in no event later
than the expiration of the option's term.

  In the case of stock purchase rights, unless the administrator determines
otherwise, the restricted stock purchase agreement must grant us a repurchase
option exercisable upon the voluntary or involuntary termination of the
purchaser's employment or consulting relationship with us for any reason,
including death or disability. The purchase price for shares repurchased
pursuant to the restricted stock purchase agreement will be the original price
paid by the purchaser and may be paid by cancellation of any indebtedness of
the purchaser to us. The repurchase option will lapse at a rate determined by
the administrator.

  The exercise price of all incentive stock options granted under the Amended
and Restated 1999 Stock Plan must be at least equal to the fair market value on
the date of grant of the common stock underlying the option. The exercise price
of nonstatutory stock options and stock purchase rights granted under the
Amended and Restated 1999 Stock Plan is determined by the administrator, but
with respect to nonstatutory stock options intended to qualify as "performance-
based compensation" within the meaning of Section 162(m) of the Code, the
exercise price must be at least equal to the fair market value on the date of
grant of the common stock underlying the option. With respect to any
participant who owns stock possessing more than 10% of the voting power of all
classes of our outstanding capital stock, the exercise price of any incentive
stock option granted must be at least equal to 110% of the fair market value on
the grant date and the term of the incentive stock option must not exceed five
years. The term of all other options granted under the Amended and Restated
1999 Stock Plan may not exceed ten years.

  The Amended and Restated 1999 Stock Plan provides that, in the event of a
merger of Mediaplex with or into another corporation, or a sale of
substantially all of our assets, each option and stock purchase right must be
assumed, or an equivalent option or stock purchase right substituted, by the
successor corporation. If the

                                       55
<PAGE>

outstanding options and stock purchase rights are not assumed or substituted
for by the successor corporation, the optionees will fully vest in and have the
right to exercise their options or stock purchase rights. If an option or stock
purchase right becomes fully vested and exercisable in the event of a merger or
sale of assets, the administrator must notify the optionee that the option or
stock purchase right will be fully exercisable for a period of 15 days from the
date of notice and that the option or stock purchase right will terminate upon
the expiration of the 15-day period.

  1999 Employee Stock Purchase Plan. Our 1999 Employee Stock Purchase Plan was
adopted by our board of directors in August 1999, and by our stockholders in
September 1999. The 1999 Employee Stock Purchase Plan will become effective
upon the closing of this offering. This plan is designed to allow our eligible
employees and the eligible employees of any participating subsidiaries to
purchase shares of common stock, at semi-annual intervals, with their
accumulated payroll deductions.

  We have reserved 400,000 shares of our common stock for issuance pursuant to
the 1999 Employee Stock Purchase Plan. In addition, commencing January 1, 2000,
the number of shares reserved for issuance under the 1999 Employee Stock
Purchase Plan will be increased by an amount equal to the least of: (a) 400,000
shares, (b) 2% of the outstanding shares on such date or (c) an amount
determined by our board of directors. As of the date of this prospectus, no
shares had been issued under the 1999 Employee Stock Purchase Plan.

  Our 1999 Employee Stock Purchase Plan, which is intended to qualify under
Section 423 of the Code, contains consecutive, overlapping, 24-month offering
periods. Each offering period includes four six-month purchase periods. The
offering periods generally start on the first trading day on or after May 1 and
November 1 of each year, except for the first offering period, which commences
on the first trading day on or after the effective date of this offering and
ends on the last trading day on or before October 31, 2001.

  Employees are eligible to participate if they are customarily employed by us
or any participating subsidiary for at least 20 hours per week and more than
five months in any calendar year. However, employees may not be granted an
option to purchase stock under the 1999 Employee Stock Purchase Plan if they
either:

  . immediately after grant, own stock possessing 5% or more of the total
    combined voting power or value of all classes of our capital stock; or

  . hold rights to purchase stock under our 1999 Employee Stock Purchase Plan
    that accrue at a rate which exceeds $25,000 worth of stock for each
    calendar year.

  The 1999 Employee Stock Purchase Plan permits each participant to purchase
our common stock through payroll deductions of up to 10% of his or her
"compensation." Compensation is defined as the participant's base straight-time
gross earnings, overtime, shift premium and bonuses, but excludes other
compensation. The maximum number of shares a participant may purchase during a
single purchase period is 1,000 shares.

  Amounts deducted and accumulated by the participant are used to purchase
shares of common stock at the end of each purchase period. The price of stock
purchased under the 1999 Employee Stock Purchase Plan is generally 85% of the
lower of the fair market value of the common stock either:

  . at the beginning of the offering period; or

  . at the end of the purchase period.

  In the event the fair market value at the end of a purchase period is less
than the fair market value at the beginning of the offering period, the
participants will be withdrawn from the current offering period following
exercise and automatically re-enrolled in a new offering period. The new
offering period will use the lower fair market value as of the first date of
the new offering period to determine the purchase price for future purchase
periods. Participants may end their participation at any time during an
offering period, and they will be paid their payroll deductions to date.
Participation ends automatically upon termination of employment with us.

                                       56
<PAGE>

  Rights granted under the 1999 Employee Stock Purchase Plan are not
transferable by a participant other than by will, the laws of descent and
distribution, or as otherwise provided under the 1999 Employee Stock Purchase
Plan. The 1999 Employee Stock Purchase Plan provides that, in the event of a
merger of Mediaplex with or into another corporation or a sale of substantially
all of our assets, each outstanding option may be assumed or substituted for by
the successor corporation. If the successor corporation refuses to assume or
substitute for the outstanding options, the offering period then in progress
will be shortened and a new exercise date will be set.

  Our board of directors has the authority to amend or terminate the 1999
Employee Stock Purchase Plan, except that no such action may adversely affect
any outstanding rights to purchase stock under the 1999 Employee Stock Purchase
Plan, provided that the board of directors may terminate an offering period on
any exercise date if the board of directors determines that the termination of
the 1999 Employee Stock Purchase Plan is in our best interests and the best
interests of our stockholders. The board of directors may in its sole
discretion amend the 1999 Employee Stock Purchase Plan to the extent necessary
and desirable to avoid unfavorable financial accounting consequences by
altering the purchase price for any offering period, shortening any offering
period or allocating remaining shares among the participants. Unless sooner
terminated by our board of directors, the 1999 Employee Stock Purchase Plan
will terminate automatically ten years from the effective date of this
offering.

401(k) Plan

  In February 1997, we adopted a 401(k) plan to provide eligible employees with
a tax preferential savings and investment program. Employees become eligible to
participate in the 401(k) plan on the first day they perform an hour of service
for us, at which point we classify them as participants. They may elect to
reduce their current compensation by up to the lesser of 15% of eligible
compensation or the statutorily prescribed annual limit, currently $10,000, and
have this reduction contributed to the 401(k) plan. The 401(k) plan permits,
but does not require, us to make additional matching contributions to the
401(k) plan on behalf of eligible participants. All contributions made by and
on behalf of participants are subject to a maximum contribution limitation
currently equal to the lesser of 25% of their compensation or $30,000 per year.
At the direction of each participant, the trustee of the 401(k) plan invests
the assets of the 401(k) plan in selected investment options. Contributions by
participants or by us to the 401(k) plan, and income earned on plan
contributions, are generally not taxable to the participants until withdrawn,
and contributions by us, if any, are generally deductible by us when made. To
date, we have made no contributions to the 401(k) plan on behalf of
participants.

Limitations on Directors' Liability and Indemnification

  Our amended and restated certificate of incorporation limits the liability of
directors to the maximum extent permitted by Delaware law. Delaware law
provides that directors of a corporation will not be personally liable for
monetary damages for breach of their fiduciary duties as directors, except
liability for any of the following:

  . any breach of their duty of loyalty to the corporation or its
    stockholders;

  . acts or omissions not in good faith or that involve intentional
    misconduct or a knowing violation of law;

  . unlawful payments of dividends or unlawful stock repurchases or
    redemptions; or

  . any transaction from which the director derived an improper personal
    benefit.

  This limitation of liability does not apply to liabilities arising under the
federal securities laws and does not affect the availability of equitable
remedies such as injunctive relief or rescission.

  Our amended and restated certificate of incorporation provides that we may
indemnify our directors, officers and employees to the fullest extent permitted
by law. We believe that indemnification under our bylaws

                                       57
<PAGE>

covers at least negligence and gross negligence on the part of indemnified
parties. Our bylaws also permit us to secure insurance on behalf of any
officer, director, employee or other agent for any liability arising out of his
or her actions in such capacity, regardless of whether our bylaws would permit
indemnification.

  We have entered into agreements to indemnify our directors and executive
officers, in addition to indemnification provided for in our bylaws. These
agreements, among other things, provide for indemnification of our directors
and executive officers for expenses, judgments, fines and settlement amounts
incurred by them in any action or proceeding arising out of their services as
directors or executive officers or at our request. We believe that these
provisions and agreements are necessary to attract and retain qualified persons
as directors and executive officers.

  At present, there is no material litigation or proceeding pending involving
any of our directors or officers in which indemnification is required or
permitted, and we are not aware of any threatened material litigation or
proceeding that might result in a claim for indemnification.

                                       58
<PAGE>

                           RELATED PARTY TRANSACTIONS

  Since our inception in September 1996, we have never been party to, and we
have no plan to be a party to, any transaction or series of similar
transactions in which the amount involved exceeded or will exceed $60,000 and
in which any director, executive officer or holder of more than 5% of our
common stock had or will have an interest, other than as described under
"Management" and the transactions described below.

Transactions with Founders

  Michael Schwartz, Eugene Jarvis, Raifman & Edwards LLP and PointBreak
Ventures, LLC were involved in our initial funding. Messrs. Schwartz and Jarvis
served as our initial officers and directors. Neither Mr. Schwartz nor Mr.
Jarvis is currently affiliated with Mediaplex.

Michael Schwartz and Eugene Jarvis

  Following our inception, in September 1996 and October 1996, we issued
2,460,000 shares of our common stock to Michael Schwartz at a purchase price of
$0.0001 per share for a total purchase price of $246 and 800,000 shares of our
common stock to Eugene Jarvis at a purchase price of $0.05 per share for a
total purchase price of $40,000. In December 1996, we issued 800,000 shares of
our common stock to Kuni Research, of which Mr. Jarvis is a stockholder, at a
purchase price of $0.05 per share for a total purchase price of $40,000, and in
January 1997, we issued an additional 800,000 shares of our common stock to
Eugene Jarvis, at a purchase price of $0.05 per share for a total purchase
price of $40,000.

  In June 1997, we issued a convertible promissory note to Michael Schwartz in
consideration for past services rendered. In June 1997, $232,161 of the
outstanding amount of the convertible promissory note was converted into
4,643,228 shares of our common stock at a conversion rate of $0.05 per share.
In April 1998, we repurchased these shares at the original conversion price of
$0.05 per share with a convertible promissory note.

Raifman & Edwards LLP

  Gregory R. Raifman and Jon L. Edwards, two of our current executive officers,
are general partners of Raifman & Edwards LLP. In September 1996, we issued
350,000 shares of our common stock to Raifman & Edwards LLP at a purchase price
of $0.0001 per share for a total purchase price of $35. In July 1997, we issued
a convertible promissory note to Raifman & Edwards LLP, in consideration for
past services rendered, for $64,569. This convertible promissory note bore
interest at a rate of 6% per annum, and had a due date of July 1999. In March
1999, Mediaplex converted the outstanding amount and accrued interest of $6,458
into 947,009 shares of our common stock at a conversion rate of $0.075 per
share for a total purchase price of $71,027. In July 1998, Michael Schwartz
transferred a convertible promissory note, issued by us, to Raifman & Edwards
LLP, which in March 1999 was converted into 4,643,228 shares of our common
stock at a conversion rate of $0.05 per share for a total purchase price of
$23,216.

  All shares initially issued to, or subsequently purchased by, Raifman &
Edwards LLP have been transferred to R&E Holdings, LLC, a limited liability
company in which Gregory R. Raifman and Jon L. Edwards are managing members.

PointBreak Ventures, LLC

  Gregory R. Raifman and Jon L. Edwards are managing members of, and hold
substantial interest in, PointBreak Ventures, LLC. Walter Haefeker, a current
executive officer, also holds a substantial interest in PointBreak Ventures,
LLC. In October 1996, we issued 250,000 shares of our common stock to
PointBreak Ventures, LLC at a purchase price of $0.0001 per share for a total
purchase price of $25.

                                       59
<PAGE>

Certain Business Relationships

  Raifman & Edwards LLP provided legal and management services to us in the
period from inception to December 31, 1996, and the years ended December 31,
1997 and 1998 of approximately $22,000, $67,000 and $197,000, respectively. No
legal services were provided by Raifman & Edwards LLP to us in the nine months
ended September 30, 1999.

  In May 1998, we entered into an oral agreement with Raifman & Edwards LLP to
sublease a portion of the office space we currently occupy at our headquarters
in San Francisco, California. The sublease terms and payments made by us to
Raifman & Edwards LLP are substantially similar to the lease terms and payments
made by Raifman & Edwards LLP to the landlord. Since May 1998, we have paid
Raifman & Edwards LLP a total of approximately $112,000 for these lease
payments.

Transactions with Management and Others

  In connection with his employment by us in January 1999, we issued a warrant
to purchase 500,000 shares of our common stock at an exercise price of $0.50
per share to Timothy M. Favia, one of our current executive officers. The
warrant may be exercised prior to January 10, 2002 by Mr. Favia.

  In connection with our acquisition of Netranscend Software, Inc. in March
1999, we issued to Ruiqing "Barclay" Jiang, one of our current executive
officers and formerly the sole shareholder of Netranscend Software, Inc., a
promissory note in the principal amount of $430,000, payable in four annual
installments and an aggregate of 1,979,000 shares of common stock valued at
$2.6 million. Of the shares issued, 300,000 are currently being held in escrow
to cover breaches of representations and warranties made by Mr. Jiang and
Netranscend Software, Inc. in the agreement and plan of reorganization executed
in connection with the acquisition.

  In February 1999, we sold an aggregate of 1,206,000 shares of Series A
preferred stock to investors at a purchase price of $1.25 per share or
$1,507,500 in the aggregate. In June 1999, we sold an aggregate of 4,500,000
shares of Series B preferred stock to investors at a purchase price of $2.00
per share or $9,000,000 in the aggregate. In August 1999, we sold an aggregate
of 4,000,000 shares of Series C preferred stock to investors at a purchase
price of $3.59 per share or $14,360,000 in the aggregate. The shares of Series
A, Series B and Series C preferred stock will automatically convert into an
aggregate of 9,706,000 shares of common stock upon the closing of this
offering. The holders of converted shares of Series C preferred stock are
entitled to demand and piggy-back registration rights. See "Description of
Capital Stock--Registration Rights."

  The investors in the preferred stock included the following entities that
hold 5% or more of our stock or that are affiliated with our directors or
executive officers, or both:

<TABLE>
<CAPTION>
                            Shares of       Shares of       Shares of    Aggregate
                            Series A        Series B        Series C      Purchase
Investor                 Preferred Stock Preferred Stock Preferred Stock   Price
- ------------------------ --------------- --------------- --------------- ----------
<S>                      <C>             <C>             <C>             <C>
5% Stockholder Entities
 Affiliated with a
 Mediaplex Director or
 Executive Officer:
 Entity affiliated with
  James DeSorrento
  (1)(2)................     160,000          140,000              --    $  480,000
 Entity affiliated with
  A. Brooke Seawell
  (1)(3)................          --           75,000              --       150,000
 Entity affiliated with
  Gregory R. Raifman and
  Jon L. Edwards
  (1)(4)................          --               --          19,360        69,502
 Entities affiliated
  with Lawrence D.
  Lenihan, Jr.(1)(5)....          --               --       1,671,309     5,999,999
Other 5% Stockholders
 Zeron Capital Ltd.
  (6)...................          --        2,625,000              --     5,250,000
 The Goldman Sachs
  Group, Inc. (7).......          --               --       1,392,758     5,000,001
</TABLE>
- --------
(1) James DeSorrento, A. Brooke Seawell, Gregory R. Raifman, Jon L. Edwards and
    Lawrence D. Lenihan, Jr. are each members of our board of directors.

(2) All shares are held of record by DeSorrento Revocable Trust under an
    agreement dated 12/17/80.

                                       60
<PAGE>

(3) All shares are held of record by Seawell Revocable Trust, A. Brooke Seawell
    & Patricia C. Seawell, trustees.

(4) All shares are held of record by R&E Holdings, LLC. Messrs. Gregory R.
    Raifman and Jon L. Edwards are the managing members and beneficial owners
    of R&E Holdings, LLC. Each of Mr. Raifman and Mr. Edwards disclaims
    beneficial ownership of these shares, except to the extent of his
    respective pecuniary interest therein.

(5) Represents 1,483,484 shares of Series C preferred stock held of record by
    Pequot Private Equity Fund, L.P. and 187,825 shares of Series C preferred
    stock held of record by Pequot Offshore Private Equity Fund, Inc. Mr.
    Lenihan is the fund manager for Pequot Capital Management, Inc. He
    disclaims beneficial ownership of these shares except to the extent of his
    pecuniary interest therein.

(6) Includes 1,500,000 shares held of record by Odyssey Venture Partners and
    1,000,000 shares held of record by Argossy Limited. Argossy Limited and
    Odyssey Venture Partners are funds affiliated with Zeron Capital Ltd. Zeron
    Capital Ltd. also holds a warrant to purchase 125,000 shares of Series B
    preferred stock.

(7) Includes 139,276 shares of Series C preferred stock purchased by Stone
    Street Fund 1999 L.P., an affiliate of The Goldman Sachs Group, Inc.

  In connection with the sale of our Series B preferred stock in June 1999, we
issued a warrant to purchase 125,000 shares of Series B preferred stock, at an
exercise price of $2.00 per share, to Zeron Capital, Ltd., a 5% stockholder.
After this offering, the warrant will be exercisable for a like number of
shares of our common stock. The warrant may be exercised at any time prior to
its expiration in June 2002.

  In connection with the sale of our Series B preferred stock in June 1999 to
Zeron Capital, Ltd., we issued a warrant to purchase 150,000 shares of Series B
preferred stock, at an exercise price of $2.00 per share, and a warrant to
purchase 100,000 shares of common stock, at a purchase price of $0.50 per
share, to Retail Ventures International, Inc., a financial advisor to us. After
this offering, the warrant to purchase Series B preferred stock will be
exercisable for a like number of shares of our common stock. The warrants may
be exercised at any time prior to their expiration in June 2002.


                                       61
<PAGE>

                             PRINCIPAL STOCKHOLDERS

  The following table sets forth information with respect to beneficial
ownership of our common stock before and after the offering by:

  . each person or entity who beneficially owns more than 5% of our common
    stock;

  . each of our named executive officers;

  . each of our directors; and

  . all executive officers and directors as a group.

  Except as otherwise noted, the address of each 5% stockholder listed in the
table is c/o Mediaplex, Inc., 131 Steuart Street, Fourth Floor, San Francisco,
California 94105. The table includes all shares of common stock issuable within
60 days of September 30, 1999, upon the exercise of options and warrants
beneficially owned by the indicated stockholders on that date based on options
and warrants outstanding as of September 30, 1999. Beneficial ownership is
determined in accordance with the rules of the Securities and Exchange
Commission and includes voting and investment power with respect to shares. To
our knowledge, except under applicable community property laws or as otherwise
indicated, the persons named in the table have sole voting and sole investment
control with respect to all shares beneficially owned. The applicable
percentage of ownership for each stockholder is based on shares of common stock
outstanding as of September 30, 1999, together with applicable options and
warrants for that stockholder. Shares of common stock issuable upon exercise of
options and warrants beneficially owned are deemed outstanding for the purpose
of computing the percentage ownership of the person holding those options and
warrants, but are not deemed outstanding for computing the percentage ownership
of any other person.

<TABLE>
<CAPTION>
                                                         Percent of
                                      Number of      Shares Outstanding
                                      Shares of      ----------------------
                                     Common Stock     Before        After
Name                              Beneficially Owned Offering     Offering
- --------------------------------- ------------------ ---------    ---------
<S>                               <C>                <C>          <C>
R & E Holdings, LLC (1)..........     10,296,265            41.6%        33.5%
Zeron Capital Ltd. (2)...........      2,625,000            10.6          8.5
 44 Church Street
 Hamilton HM12
 Bermuda
Pequot Capital Management, Inc.
 (3).............................      1,671,309             6.8          5.4
 500 Nyala Farm Road
 Westport, CT 06880
The Goldman Sachs Group, Inc.
 (4).............................      1,392,758             5.6          4.5
 85 Broad Street
 New York, NY 10002
Gregory R. Raifman (5)...........     12,296,265            46.5         37.9
Jon L. Edwards (6)...............     12,046,265            45.9         37.4
Ruiqing "Barclay" Jiang (7)......      2,002,833             8.1          6.5
Walter Haefeker (8)..............      1,125,000             4.4          3.5
Lawrence D. Lenihan, Jr. (9).....      1,671,309             6.8          5.4
James DeSorrento (10)............        350,000             1.4          1.1
A. Brooke Seawell (11)...........        125,000               *            *
Peter S. Sealey (12).............         50,000               *            *
All executive officers and
 directors as a group (13
 persons) (13)...................     19,156,518            65.6         54.4
</TABLE>
- --------
  *Less than 1%
 (1) Messrs. Raifman and Edwards are the managing members and the beneficial
     owners of R&E Holdings, LLC.

 (2) Includes 1,500,000 shares held of record by Odyssey Venture Partners and
     1,000,000 shares held of record by Argossy Limited. Odyssey Venture
     Partners and Argossy Limited are venture funds affiliated with Zeron
     Capital Ltd. Also includes a warrant held by Zeron Capital Ltd. to
     purchase 125,000 shares.

                                       62
<PAGE>

 (3) Represents 1,483,484 shares held of record by Pequot Private Equity Fund,
     L.P. and 187,825 shares held of record by Pequot Offshore Private Equity
     Fund, Inc. Pequot Private Equity Fund, L.P. and Pequot Offshore Private
     Equity Fund, Inc. are managed by Pequot Capital Management, Inc.

 (4) Includes 139,276 shares held of record by Stone Street Fund 1999, L.P., an
     affiliate of The Goldman Sachs Group, Inc.

 (5) Represents 10,296,265 shares held of record by R&E Holdings, LLC, 250,000
     shares held of record by PointBreak Ventures, LLC and 1,750,000 shares
     issuable upon the exercise of options exercisable within 60 days of
     September 30, 1999. Mr. Raifman is one of the beneficial owners of R&E
     Holdings, LLC and PointBreak Ventures, LLC. Mr. Raifman disclaims
     beneficial interest of the shares held by R&E Holdings, LLC and PointBreak
     Ventures, LLC, except to the extent of his pecuniary interest in those
     entities.

 (6) Represents 10,296,265 shares held of record by R&E Holdings, LLC, 250,000
     shares held of record by PointBreak Ventures, LLC and 1,500,000 shares of
     common stock issuable upon the exercise of options exercisable within 60
     days of September 30, 1999. Mr. Edwards is one of the beneficial owners of
     R&E Holdings, LLC and PointBreak Ventures, LLC. Mr. Edwards disclaims
     beneficial interest of the shares held by R&E Holdings, LLC and PointBreak
     Ventures, LLC, except to the extent of his pecuniary interest in those
     entities.

 (7) Includes 23,833 shares issuable upon the exercise of options exercisable
     within 60 days of September 30, 1999.

 (8) Represents 1,125,000 shares issuable upon the exercise of options
     exercisable within 60 days of September 30, 1999.

 (9) Represents 1,671,309 shares beneficially owned by Pequot Capital
     Management, Inc. See note (3). Mr. Lenihan is the fund manager of Pequot
     Capital Management, Inc. Mr. Lenihan disclaims beneficial ownership of
     these shares, except to the extent of his pecuniary interest in that
     entity.

(10) Represents 300,000 shares held of record by DeSorrento Revocable Trust, of
     which Mr. DeSorrento is the beneficial owner, and 50,000 shares held by
     Mr. DeSorrento.
(11) Represents 75,000 shares held of record by Seawell Revocable Trust, A.
     Brooke Seawell & Patricia C. Seawell, trustees, and 50,000 shares held by
     Mr. Seawell. Mr. Seawell is one of the beneficial owners of the Seawell
     Revocable Trust.

(12) Represents 50,000 shares issuable upon the exercise of options exercisable
     within 60 days of September 30, 1999.

(13) See notes (5) through (12). Includes an aggregate of 4,098,833 shares
     issuable upon exercise of options held by our executive officers and
     directors exercisable within 60 days of September 30, 1999.

                                       63
<PAGE>

                          DESCRIPTION OF CAPITAL STOCK

General

  Our restated certificate of incorporation, which will become effective upon
the closing of this offering, authorizes the issuance of up to 150,000,000
shares of common stock, par value $0.0001 per share, and 10,000,000 shares of
undesignated preferred stock, par value $0.0001 per share, the rights and
preferences of which may be established from time to time by our board of
directors. As of September 30, 1999, we had outstanding 15,011,365 shares of
common stock and 9,706,000 shares of redeemable convertible preferred stock,
which will automatically convert into 9,706,000 shares of common stock upon the
completion of this offering. As of September 30, 1999, we had 122 stockholders.

Common Stock

  Each holder of common stock will be entitled to one vote for each share on
all matters to be voted upon by the stockholders, and there will be no
cumulative voting rights. Subject to preferences to which holders of preferred
stock issued after the sale of the common stock in this offering may be
entitled, holders of common stock will be entitled to receive ratably any
dividends that may be declared from time to time by the board of directors out
of funds legally available for that purpose. Please see "Dividend Policy." In
the event of our liquidation, dissolution or winding up, holders of our common
stock will be entitled to share in our assets remaining after the payment of
liabilities and the satisfaction of any liquidation preference granted to the
holders of any outstanding shares of preferred stock. Holders of common stock
have no preemptive or conversion rights or other subscription rights and there
are no redemption or sinking fund provisions applicable to the common stock.
All outstanding shares of common stock are, and the shares of common stock
offered by us in this offering, when issued and paid for, will be, fully paid
and nonassessable. The rights, preferences and privileges of the holders of
common stock are subject to, and may be adversely affected by, the rights of
the holders of shares of any series of preferred stock that we may designate in
the future.

Preferred Stock

  Upon the closing of this offering, the board of directors will be authorized,
subject to any limitations prescribed by law, without stockholder approval,
from time to time to issue up to an aggregate of 10,000,000 shares of preferred
stock, par value $0.0001 per share, in one or more series, each series to have
rights and preferences, including voting rights, dividend rights, conversion
rights, redemption privileges and liquidation preferences, as may be determined
by the board of directors. The rights of the holders of common stock will be
subject to, and may be adversely affected by, the rights of holders of any
preferred stock that may be issued in the future. The issuance of preferred
stock, while providing desirable flexibility in connection with possible
acquisitions and other corporate purposes, could have the effect of making it
more difficult for a third party to acquire, or of discouraging a third party
from attempting to acquire, a majority of our outstanding voting stock. We have
no present plans to issue any shares of preferred stock.

Warrants

  At September 30, 1999, there were outstanding warrants to purchase up to
275,000 shares of Series B preferred stock at an exercise price of $2.00 per
share and warrants to purchase up to 600,000 shares of common stock at an
exercise price of $0.50 per share. Upon completion of this offering, the
warrants to purchase shares of Series B preferred stock will become exercisable
to purchase 275,000 shares of common stock.

Registration Rights

  The holders of 4,000,000 shares of Series C preferred stock, referred to as
"registrable securities," are entitled to certain rights with respect to
registration of such shares under the Securities Act. These rights are provided
under the terms of an investor rights agreement between us and the holders of
registrable securities.

                                       64
<PAGE>

Beginning 180 days following the date of this prospectus, holders of least 25%
of the then outstanding registrable securities may require on up to two
occasions that we register for public resale at least 25% of their registrable
securities or a lesser amount, provided that the aggregate proceeds of that
offering would exceed $5.5 million. We need not register these shares if the
requested registration would occur within six months following the effective
date of any other registration statement we have filed. Also, we may defer the
registration of these shares for up to 120 days if, in the good faith judgment
of our board of directors, it would be seriously detrimental to us and our
stockholders for the registration statement to be filed. Also, holders of
registrable securities may require once per 12-month period that we register
their shares for public resale on Form S-3 or similar short-form registration,
provided we are eligible to use that form, if the value of the securities to be
registered is at least $1.0 million; however, we may defer this registration
for 120 days in view of market conditions. Furthermore, in the event we elect
to register any of our shares of common stock for purposes of effecting any
public offering, the holders of registrable securities are entitled to include
their shares of common stock in the registration, but we may reduce the number
of shares proposed to be registered in view of market conditions. All expenses
in connection with any registration, other than underwriting discounts and
commissions, will be borne by us. All registration rights will terminate five
years following the consummation of this offering, or, with respect to each
holder of registrable securities, at the time the holder is entitled to sell
all of its shares in any three-month period under Rule 144 of the Securities
Act.

Anti-Takeover Effects of Our Certificate of Incorporation and Bylaws and
Delaware Law

  Certain provisions of Delaware law and our amended and restated certificate
of incorporation and bylaws could make the following more difficult:

  . the acquisition of us by means of a tender offer;

  . the acquisition of us by means of a proxy contest or otherwise; or

  . the removal of our incumbent officers and directors.

  These provisions, summarized below, are expected to discourage certain types
of coercive takeover practices and inadequate takeover bids. These provisions
are also designed to encourage persons seeking to acquire control of us to
negotiate first with our board. We believe that the benefits of increased
protection of our potential ability to negotiate with the proponent of an
unfriendly or unsolicited proposal to acquire or restructure us outweigh the
disadvantages of discouraging such proposals because negotiation of these
proposals could result in an improvement of their terms.

  Election and Removal of Directors. Our board of directors is divided into
three classes. The directors in each class will serve for a three-year term,
one class being elected each year by our stockholders. For more information on
the classified board, see the section entitled "Management--Board of
Directors." This system of electing and removing directors may tend to
discourage a third party from making a tender offer or otherwise attempting to
obtain control of us because it generally makes it more difficult for
stockholders to replace a majority of the directors.

  Stockholder Meetings. Under our bylaws, only the board of directors, the
chairman of the board, the chief executive officer and the president may call
special meetings of stockholders.

  Requirements for Advance Notification of Stockholder Nominations and
Proposals. Our bylaws establish advance notice procedures with respect to
stockholder proposals and the nomination of candidates for election as
directors, other than nominations made by or at the direction of the board of
directors or a committee of the board.

  Delaware Anti-Takeover Law. We are subject to Section 203 of the Delaware
General Corporation Law, an anti-takeover law. In general, Section 203
prohibits a publicly held Delaware corporation from engaging in a business
combination with an interested stockholder for a period of three years
following the date the person became an interested stockholder, unless the
business combination or the transaction in which the person

                                       65
<PAGE>

became an interested stockholder is approved in a prescribed manner. Generally,
a business combination includes a merger, asset or stock sale, or other
transaction resulting in a financial benefit to the interested stockholder.
Generally, an interested stockholder is a person who, together with affiliates
and associates, owns, or within three years prior to the determination of
interested stockholder status did own, 15% or more of a corporation's voting
stock. The existence of this provision may have an anti-takeover effect with
respect to transactions not approved in advance by the board of directors,
including discouraging attempts that might result in a premium over the market
price for the shares of common stock held by stockholders.

  Elimination of Stockholder Action By Written Consent. Our certificate of
incorporation eliminates the right of stockholders to act by written consent
without a meeting.

  Elimination of Cumulative Voting. Our certificate of incorporation and bylaws
do not provide for cumulative voting in the election of directors.

  Undesignated Preferred Stock. The authorization of undesignated preferred
stock makes it possible for the board of directors to issue preferred stock
with voting or other rights or preferences that could impede the success of any
attempt to change control of us. These and other provisions may have the effect
of deferring hostile takeovers or delaying changes in control or management of
us.

  Amendment of Charter Provisions. The amendment of any of the above provisions
would require approval by holders of at least 66 2/3% of the outstanding common
stock.

Transfer Agent and Registrar

  The transfer agent and registrar for our common stock is ChaseMellon
Shareholder Services.

Nasdaq National Market Listing

  We propose to list our common stock on the Nasdaq National Market under the
symbol "MPLX."

                                       66
<PAGE>

                        SHARES ELIGIBLE FOR FUTURE SALE

  Sales of substantial amounts of our common stock in the public market after
the offering could adversely affect the market price of our common stock and
our ability to raise equity capital in the future on terms favorable to us.

  After this offering, 30,717,365 shares of our common stock will be
outstanding, assuming that the underwriters do not exercise the over-allotment
option, and based on shares outstanding as of September 30, 1999. Of these
shares, all of the 6,000,000 shares sold in this offering will be freely
tradable without restriction or further registration under the Securities Act,
unless these shares are purchased by "affiliates" as that term is defined in
Rule 144 under the Securities Act. The remaining shares of common stock held by
existing stockholders are "restricted securities" as that term is defined in
Rule 144 under the Securities Act. Restricted securities may be sold in the
public market only if registered or if they qualify for an exemption from
registration under Rule 144 or 701 under the Securities Act, which rules are
summarized below.

  As a result of the contractual restrictions described below and the
provisions of Rules 144, 144(k) and 701, the 24,717,365 restricted shares will
be available for sale in the public market as follows:

         Eligibility of Restricted Shares for Sale in the Public Market

<TABLE>
   <S>                                                                <C>
   At the effective date.............................................     55,000
   90 days after the effective date..................................     75,814
   180 days after the effective date................................. 15,826,551
   More than 180 days after the effective date.......................  8,760,000
</TABLE>

  Resale of 14,671,574 of the restricted shares that will become available for
sale in the public market will be limited by volume and other resale
restrictions under Rule 144 because the holders are our affiliates.

Rule 144

  In general, under Rule 144 as currently in effect, beginning 90 days after
the date of this prospectus, a person who has beneficially owned shares of our
common stock for at least one year is entitled to sell, within any three-month
period, a number of shares that is not more than the greater of:

  . 1% of the number of shares of common stock then outstanding, which will
    equal approximately 307,000 shares immediately after this offering; or

  . the average weekly trading volume of our common stock on the Nasdaq
    National Market during the four calendar weeks before a notice of the
    sale on Form 144 is filed.

  Sales under Rule 144 are also subject to manner of sale provisions, notice
requirements and the availability of current public information about us.

  Under Rule 144(k), a person who has not been one of our affiliates at any
time during the three months before a sale, and who has beneficially owned the
restricted shares for at least two years, is entitled to sell the shares
without complying with the manner of sale, public information, volume
limitation or notice provisions of Rule 144.

Rule 701

  In general, under Rule 701 of the Securities Act as currently in effect, any
of our employees, consultants or advisors who purchase shares from us under a
stock option plan or other written agreement can resell those shares 90 days
after the effective date of this offering in reliance on Rule 144, but without
complying with some of the restrictions, including the holding period,
contained in Rule 144.

                                       67
<PAGE>

Lock-Up Arrangements

  Holders of a total of 24,416,551 shares of common stock (including preferred
stock convertible into common stock and including all stock held by executive
officers and directors), warrants to purchase a total of 875,000 shares of
common stock and options to purchase a total of 8,205,701 shares of common
stock have agreed not to sell or otherwise dispose of any unrestricted shares
of common stock for a period of 180 days after the date of this prospectus
without the prior written consent of Lehman Brothers Inc. In addition, all
options granted under our Amended and Restated 1999 Stock Plan are subject to
similar lock-up arrangements pursuant to an agreement between the optionee and
us.

                                       68
<PAGE>

                                  UNDERWRITING

  Under the underwriting agreement, which is filed as an exhibit to the
registration statement relating to this prospectus, each of the underwriters
named below, for whom Lehman Brothers Inc., SG Cowen Securities Corporation,
U.S. Bancorp Piper Jaffray Inc. and Fidelity Capital Markets, a division of
National Financial Services Corporation, are acting as representatives, has
agreed to purchase from us the number of shares of common stock shown opposite
its name below:

<TABLE>
<CAPTION>
                                                                     Number of
     Underwriters                                                     Shares
     ------------                                                    ---------
     <S>                                                             <C>
       Lehman Brothers Inc..........................................
       SG Cowen Securities Corporation..............................
       U.S. Bancorp Piper Jaffray Inc. .............................
       Fidelity Capital Markets, a division of National Financial
        Services Corporation........................................
                                                                     ---------
       Total........................................................ 6,000,000
                                                                     =========
</TABLE>

  The underwriting agreement provides that the underwriters' obligations to
purchase shares of common stock depend on the satisfaction of the conditions
contained in the underwriting agreement. It also provides that, if any of the
shares of common stock are purchased by the underwriters under the underwriting
agreement, all of the shares of common stock that the underwriters have agreed
to purchase under the underwriting agreement must be purchased. The conditions
contained in the underwriting agreement include the requirement that:

  . the representations and warranties made by us to the underwriters are
    true;

  . there is no material change in the financial markets; and

  . we deliver to the underwriters customary closing documents.

  The representatives have advised us that the underwriters propose to offer
the shares of common stock directly to the public at the public offering price
set forth on the cover page of this prospectus. The representatives have also
advised us that the underwriters propose to offer the shares of common stock to
dealers, which may include the underwriters, at this public offering price less
a selling concession not in excess of $     per share. The underwriters may
allow, and the dealers may reallow, a concession not in excess of $     per
share to brokers and dealers. After the offering, the underwriters may change
the offering price and other selling terms.

  We have granted to the underwriters an option to purchase up to 900,000
additional shares of common stock, exercisable solely to cover over-allotments,
if any, at the public offering price less the underwriting discount shown on
the cover page of this prospectus. The underwriters may exercise this option at
any time until 30 days after the date of the underwriting agreement. If this
option is exercised, each underwriter will be committed, so long as the
conditions of the underwriting agreement are satisfied, to purchase a number of
additional shares of common stock proportionate to the underwriter's initial
commitment as indicated in the table above and we will be obligated, under the
over-allotment option, to sell the shares of common stock to the underwriters.

  We have agreed, that, without the prior consent of Lehman Brothers Inc., we
will not, with limited exceptions, directly or indirectly, offer, sell or
otherwise dispose of any shares of common stock or any securities that may be
converted into or exchanged for any shares of common stock for a period of 180
days from the date of this prospectus. All of our executive officers and
directors, stockholders holding 24,416,551 shares of our capital stock,
including our preferred stock, and holders of options and warrants to purchase
9,080,701 shares, have agreed under lock-up agreements that, without the prior
written consent of Lehman Brothers Inc., they will not, directly or indirectly,
offer, sell or otherwise dispose of any shares of common stock or any
securities that may be converted into or exchanged for any shares of common
stock for the period ending 180 days after the date of this prospectus. See
"Shares Eligible for Future Sale."


                                       69
<PAGE>

  The underwriting discount is equal to the public offering price per share of
common stock less the amount paid by the underwriters to us per share of common
stock. The underwriting discount is expected to be approximately 7% of the
public offering price. We have agreed to pay the underwriters the following
total amount, assuming either no exercise or full exercise by the underwriters
of their over-allotment option:

<TABLE>
<CAPTION>
                                                      Total Fees
                                         -------------------------------------
                                   Fee    Without Exercise  With Full Exercise
                                   Per   of Over- Allotment of Over-Allotment
                                  Share        Option             Option
                                  ------ ------------------ ------------------
<S>                               <C>    <C>                <C>
Underwriting discount paid by
 Mediaplex....................... $            $                  $
</TABLE>

  In addition, we estimate that our share of the total expenses of this
offering, excluding the underwriting discount, will be approximately
$1,050,000.

  Before this offering, there has been no public market for the shares of
common stock. The initial public offering price will be negotiated between the
representatives and us. In determining the initial public offering price of the
common stock, the representatives will consider, among other things and in
addition to prevailing market conditions, the following primary factors:

  . our historical performance and capital structure;

  . estimates of our business potential and earning prospects;

  . an overall assessment of our management; and

  . the above factors in relation to market valuations of companies in
    related businesses.

  We propose to list our common stock on the Nasdaq National Market under the
symbol "MPLX."

  Fidelity Capital Markets, a division of National Financial Services
Corporation, is acting as an underwriter in this offering, and will be
facilitating electronic distribution of information through the Internet,
Intranet and other proprietary electronic technology.

  Fidelity utilizes proprietary Internet, intranet and pager communications
technology to inform its investors of the commencement of an offering and the
availability of the preliminary prospectus. It places deal-specific information
on the Rule 134-compliant "New Issue Equity Calendar" Web page contained within
the Fidelity.com Web site. This information is presented in template format and
directs interested and eligible Fidelity customers either to contact a
dedicated Fidelity representative or to go (via hyperlink) to the Fidelity
Electronic Notification Services to download an electronic version of the
preliminary prospectus.

  After delivery of the preliminary prospectus (electronically or otherwise),
eligible Fidelity investors are able to submit conditional "offers-to-buy"
using only dedicated telephone representatives. Customers cannot place
conditional offers online. All eligible Fidelity customers who have placed
conditional offers-to-buy must confirm their original conditional offers-to-buy
with a dedicated Fidelity representative on the expected pricing date.

  Fidelity facilitates electronic delivery of preliminary prospectuses by using
a Web-based delivery platform. The preliminary prospectuses are made available
for online viewing and downloading in the widely-used electronic Adobe's
Portable Document Format. This Web platform is made available to all Fidelity
brokerage customers, who may sign-on to this Web site by using the same "sign-
on" password that allows them to access account, portfolio and other types of
client-specific information. In order to access the prospectus, the customer is
presented with disclosure information consistent with appropriate disclosure of
risk and with relevant regulatory requirements such as consent to electronic
delivery. The prospectus download/viewing screen is made available upon
customer consent to this disclosure information. Upon download and viewing of
the prospectus, a permanent record of this event is made in Fidelity's internal
systems, in similar fashion to the audit trails that are maintained for
traditional telephone and mail-based events.

                                       70
<PAGE>

  We have agreed to indemnify the underwriters against liabilities, including
liabilities under the Securities Act and liabilities arising from breaches of
the representations and warranties contained in the underwriting agreement, and
to contribute to payments that the underwriters may be required to make for
these liabilities.

  Until the distribution of the common stock is completed, rules of the
Securities and Exchange Commission may limit the ability of the underwriters
and selling group members to bid for and purchase shares of common stock. As an
exception to these rules, the representatives are permitted to engage in
transactions that stabilize the price of the common stock. These transactions
may consist of bids or purchases for the purposes of pegging, fixing or
maintaining the price of the common stock.

  The underwriters may create a short position in the common stock in
connection with the offering. This means that they may sell more shares than
are set forth on the cover page of this prospectus. If the underwriters create
a short position, then the representatives may reduce that short position by
purchasing common stock in the open market. The representatives also may elect
to reduce any short position by exercising all or part of the over-allotment
option.

  The representatives also may impose a penalty bid on underwriters and selling
group members. This means that, if the representatives purchase shares of
common stock in the open market to reduce the underwriters' short position or
to stabilize the price of the common stock, they may reclaim the amount of the
selling concession from the underwriters and selling group members that sold
those shares as part of the offering.

  In general, purchases of a security for the purpose of stabilization or to
reduce a syndicate short position could cause the price of the security to be
higher than it might otherwise be in the absence of these purchases. The
imposition of a penalty bid might have an effect on the price of a security to
the extent that it were to discourage resales of the security by purchasers in
an offering.

  Neither we nor any of the underwriters makes any representation or prediction
as to the direction or magnitude of any effect that the transactions described
above may have on the price of the common stock. In addition, neither we nor
any of the underwriters makes any representation that the representatives will
engage in these transactions or that these transactions, once commenced, will
not be discontinued without notice.

  Any offers in Canada will be made only under an exemption from the
requirements to file a prospectus in the relevant province of Canada in which
the sale is made.

  Purchasers of the shares of common stock offered in this prospectus may be
required to pay stamp taxes and other charges under the laws and practices of
the country of purchase, in addition to the offering price listed on the cover
page of this prospectus.

  The representatives have informed us that they do not intend to confirm sales
to discretionary accounts that exceed 5% of the shares of common stock offered
by them.

  At our request, the underwriters have reserved up to 300,000 shares of the
common stock offered by this prospectus for sale to our officers, directors,
employees and their family members and to our business associates at the
initial public offering price set forth on the cover page of this prospectus,
which shares shall not be subject to the lockup agreements described above.
These persons must commit to purchase no later than the close of business on
the day following the date of this prospectus. The number of shares available
for sale to the general public will be reduced to the extent these persons
purchase the reserved shares.

                                       71
<PAGE>

                                 LEGAL MATTERS

  The validity of the shares of common stock offered hereby will be passed upon
for us by Wilson Sonsini Goodrich & Rosati, Professional Corporation, Palo
Alto, California. Fenwick & West LLP, Palo Alto, California will pass upon
legal matters for the underwriters. As of the date of this prospectus, WS
Investments, an investment partnership composed of certain current and former
members of and persons associated with Wilson Sonsini Goodrich & Rosati,
Professional Corporation, and certain individual attorneys of this firm,
beneficially own a total of 43,116 shares of our common stock.

                                    EXPERTS

  The financial statements of Mediaplex, Inc., as of December 31, 1998 and
1997, for each of the two years in the period ended December 31, 1998, and for
the period from September 10, 1996 (inception) to December 31, 1996 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 accounting and auditing.

  The financial statements of Netranscend Software, Inc. (a development stage
company) as of December 31, 1998 and 1997, for each of two years in the period
ended December 31, 1998, and for the period from November 27, 1996 (inception)
to December 31, 1998 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 accounting and auditing.

                      WHERE YOU CAN FIND MORE INFORMATION

  We have filed with the Securities and Exchange Commission under the
Securities Act a registration statement on Form S-1, including the exhibits
filed with the registration statement, with respect to the shares to be sold in
this offering. This prospectus does not contain all the information contained
in the registration statement. For further information with respect to us and
the shares to be sold in this offering, we refer you to the registration
statement. Statements contained in this prospectus as to the contents of any
contract, agreement or other document to which we make reference are not
necessarily complete. In each instance, we refer you to the copy of the
contract, agreement or other document filed as an exhibit to the registration
statement, each statement being qualified in all respects by the more complete
description of the matter involved.

  You may read and copy all or any portion of the registration statement or any
reports, statements or other information we file at the Commission's public
reference room 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 500 West
Madison Street, Suite 1400, Chicago, Illinois 60661. You can request copies of
these documents upon payment of a duplicating fee by writing to the Commission.
Please call the Commission at 1-800-SEC-0330 for further information on the
operation of the public reference rooms. Our Commission filings, including the
registration statement, will also be available to you on the Commission's
Internet site, http://www.sec.gov.

  We intend to send to our stockholders annual reports containing audited
consolidated financial statements and quarterly reports containing unaudited
financial statements for the first three quarters of each fiscal year.

                                       72
<PAGE>

                                Mediaplex, Inc.

                         Index to Financial Statements

<TABLE>
<CAPTION>
                                                                           Pages
                                                                           -----
<S>                                                                        <C>
MEDIAPLEX, INC.
Report of Independent Accountants.........................................  F-2
Balance Sheets............................................................  F-3
Statements of Operations..................................................  F-4
Statements of Changes in Stockholders' Equity (Deficit)...................  F-5
Statements of Cash Flows..................................................  F-6
Supplemental Disclosure of Cash Flows.....................................  F-7
Notes to Financial Statements.............................................  F-8
</TABLE>

<TABLE>
<S>                                                                        <C>
PRO FORMA FINANCIAL INFORMATION
Overview.................................................................. F-22
Pro Forma Statement of Operations--Year Ended December 31, 1998........... F-23
Pro Forma Statement of Operations--Nine Months Ended September 30, 1999... F-24
Notes to Pro Forma Financial Information.................................. F-25
NETRANSCEND SOFTWARE, INC.
Report of Independent Accountants......................................... F-26
Balance Sheets............................................................ F-27
Statements of Operations.................................................. F-28
Statements of Shareholders' Equity (Deficit).............................. F-29
Statements of Cash Flows.................................................. F-30
Notes to Financial Statements............................................. F-31
</TABLE>

                                      F-1
<PAGE>

                       Report of Independent Accountants

To the Board of Directors and Stockholders of Mediaplex, Inc.

The recapitalization described in Note 1 to the financial statements has not
been consummated at November 11, 1999. When it has been consummated, we will be
in a position to furnish the following report:

  "In our opinion, the accompanying financial statements present fairly, in all
material respects, the financial position of Mediaplex, Inc. (the "Company") at
December 31, 1997 and 1998, and the results of its operations and its cash
flows for the period from September 10, 1996 (inception) to December 31, 1996
and the years ended December 31, 1997 and 1998, 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 audits. We conducted our
audits 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
audits provide a reasonable basis for the opinion expressed above."

/s/ PricewaterhouseCoopers LLP

San Francisco, California
July 30, 1999
except for Note 10,
which is as of
September 1, 1999


                                      F-2
<PAGE>

                                Mediaplex, Inc.

                                 Balance Sheets

<TABLE>
<CAPTION>
                                             December 31,
                                        ------------------------  September 30,
                                           1997         1998          1999
                                        -----------  -----------  -------------
                                                                   (unaudited)
<S>                                     <C>          <C>          <C>
Assets
Current Assets:
  Cash and cash equivalents...........  $   141,994  $   374,567  $ 16,519,632
  Accounts receivable, net of
   allowance of $20,211, $37,367 and
   $1,245,161 as of December 31, 1997
   and 1998 and September 30, 1999,
   respectively.......................        3,967      936,497     5,415,672
  Other current assets................           --           --       274,367
                                        -----------  -----------  ------------
   Total current assets...............      145,961    1,311,064    22,209,671
  Property and equipment, net.........      110,546      105,921     1,844,330
  Goodwill and intangible assets, net
   of accumulated amortization of
   $502,378 as of September 30, 1999..           --           --     2,508,113
  Other assets........................        5,000       27,030       929,485
                                        -----------  -----------  ------------
   Total assets.......................  $   261,507  $ 1,444,015  $ 27,491,599
                                        ===========  ===========  ============
Liabilities and Stockholders' Equity
 (Deficit)
Current Liabilities:
  Accounts payable....................  $   379,122  $ 1,528,600  $    608,653
  Payables to stockholders............       48,873      139,701        77,281
  Advance from stockholder............           --      262,750            --
  Accrued liabilities.................      150,067      422,177     5,112,688
  Deferred revenues...................      142,400      479,764     1,558,251
  Notes payable to stockholders,
   current portion....................           --      339,569       110,000
  Capital lease obligations, current
   portion............................       11,463           --            --
  Other liabilities...................           --        1,039            --
                                        -----------  -----------  ------------
   Total current liabilities..........      731,925    3,173,600     7,466,873
Notes payable to stockholders.........       64,569      232,161       262,765
Capital lease obligations.............       23,072           --            --
                                        -----------  -----------  ------------
   Total liabilities..................      819,566    3,405,761     7,729,638
                                        -----------  -----------  ------------
Commitments (Note 6)
Stockholders' Equity (Deficit):
  Convertible preferred stock;
   issuable in series; $0.0001 par
   value; authorized 9,981,000 shares;
   9,706,000 shares issued and
   outstanding; liquidation preference
   of $24,867,500 as of September 30,
   1999...............................           --           --           971
  Common stock, $0.0001 par value;
   authorized 10,000,000, 40,000,000,
   and 75,000,000 shares,
   respectively; 11,318,566, 6,983,628
   and 15,011,365 shares issued and
   outstanding as of December 31, 1997
   and 1998 and September 30, 1999,
   respectively.......................        1,132          698         1,500
  Additional paid-in capital..........      813,355    1,482,685    38,915,139
  Warrants............................           --           --     2,472,354
  Beneficial conversion feature.......           --           --    14,360,000
  Deferred stock compensation.........           --      (53,371)   (5,596,461)
  Accumulated deficit.................   (1,372,546)  (3,391,758)  (30,391,542)
                                        -----------  -----------  ------------
   Total stockholders' equity
    (deficit).........................     (558,059)  (1,961,746)   19,761,961
                                        -----------  -----------  ------------
   Total liabilities and stockholders'
    equity (deficit)..................  $   261,507  $ 1,444,015  $ 27,491,599
                                        ===========  ===========  ============
</TABLE>

   The accompanying notes are an integral part of these financial statements.

                                      F-3
<PAGE>

                                Mediaplex, Inc.

                            Statements of Operations

<TABLE>
<CAPTION>
                          September 10,
                               1996            Years Ended            Nine Months Ended
                          (inception) to      December 31,              September 30,
                           December 31,  ------------------------  -------------------------
                               1996         1997         1998         1998          1999
                          -------------- -----------  -----------  -----------  ------------
                                                                   (unaudited)  (unaudited)
<S>                       <C>            <C>          <C>          <C>          <C>
Revenues................    $      --    $   425,877  $ 3,588,094   $2,590,895   $13,940,808
Cost of revenues........           --        445,372    2,770,567    1,968,773    10,948,571
                            ---------    -----------  -----------  -----------  ------------
  Gross profit (loss)...           --        (19,495)     817,527      622,122     2,992,237
                            ---------    -----------  -----------  -----------  ------------

Operating expenses:
  Sales and marketing...       22,704        480,756      819,641      481,626     3,523,109
  Research and
   development..........       48,834        347,130      555,736      415,003     2,203,039
  General and
   administrative.......       30,948        256,413      636,651      457,073     2,885,701
  Stock-based
   compensation.........      152,694         11,000      577,525      151,427     6,705,252
  Amortization of
   goodwill and
   intangibles..........           --             --           --           --       502,378
                            ---------    -----------  -----------  -----------  ------------
    Total operating
     expenses...........      255,180      1,095,299    2,589,553    1,505,129    15,819,479
                            ---------    -----------  -----------  -----------  ------------
    Loss from
     operations.........     (255,180)    (1,114,794)  (1,772,026)    (883,007)  (12,827,242)
Interest income
 (expense), net.........           --         (2,572)    (247,186)    (233,934)      187,458
                            ---------    -----------  -----------  -----------  ------------
  Net loss..............     (255,180)    (1,117,366)  (2,019,212)  (1,116,941)  (12,639,784)
Beneficial conversion
 feature of Series C
 convertible preferred
 stock                             --             --           --           --    14,360,000
                            ---------    -----------  -----------  -----------  ------------
Net loss attributable to
 common stockholders....    $(255,180)   $(1,117,366) $(2,019,212) $(1,116,941) $(26,999,784)
                            =========    ===========  ===========  ===========  ============
Net loss per share--
 basic and diluted......    $   (0.07)   $     (0.13) $     (0.25) $     (0.13) $      (2.05)
                            =========    ===========  ===========  ===========  ============
Weighted average shares
 used to compute net
 loss per share--basic
 and diluted............    3,795,714      8,457,464    8,186,127    8,591,365    13,074,428
                            =========    ===========  ===========  ===========  ============
Pro forma net loss per
 share--basic and
 diluted (unaudited)....                              $     (0.25)              $      (1.56)
                                                      ===========               ============
Weighted average shares
 used to compute pro
 forma net loss per
 share--basic and
 diluted (unaudited)....                                8,186,127                 17,280,523
                                                      ===========               ============
</TABLE>

   The accompanying notes are an integral part of these financial statements.

                                      F-4
<PAGE>

                                Mediaplex, Inc.

            Statements of Changes in Stockholders' Equity (Deficit)

<TABLE>
<CAPTION>
                    Convertible
                  Preferred Stock    Common Stock      Additional   Beneficial               Deferred
                  ---------------- ------------------    Paid-in    Conversion                Stock      Accumulated
                   Shares   Amount   Shares    Amount    Capital      Feature    Warrants  Compensation    Deficit
                  --------- ------ ----------  ------  -----------  ----------- ---------- ------------  ------------
<S>               <C>       <C>    <C>         <C>     <C>          <C>         <C>        <C>           <C>
Balance,
September 10,
1996
(inception).....         --  $ --          --  $   --  $        --  $        -- $       -- $        --   $         --
Issuance of
common stock for
cash and for
services........                    3,060,000     306      152,419
Issuance of
common stock....                    1,600,000     160       79,840
Net loss........                                                                                             (255,180)
                  ---------  ----  ----------  ------  -----------  ----------- ---------- -----------   ------------
Balance,
December 31,
1996............         --    --   4,660,000     466      232,259           --         --          --       (255,180)
Issuance of
common stock....                    1,795,338     180      338,421
Conversion of
payable to
stockholder for
common stock....                    4,643,228     464      231,697
Issuance of
common stock for
services........                      220,000      22       10,978
Net loss........                                                                                           (1,117,366)
                  ---------  ----  ----------  ------  -----------  ----------- ---------- -----------   ------------
Balance,
December 31,
1997............         --    --  11,318,566   1,132      813,355           --         --          --     (1,372,546)
Repurchase of
common stock for
convertible note
payable.........                   (4,643,228)   (464)    (231,697)
Beneficial
conversion
feature of note
payable to
stockholder.....                                           232,161
Issuance of
common stock....                       76,000       7       37,993
Issuance of
common stock for
services........                      232,290      23      151,404
Stock-based
compensation....                                           286,079
Deferred stock
compensation....                                           193,390                            (193,390)
Amortization of
deferred stock
compensation....                                                                               140,019
Net loss........                                                                                           (2,019,212)
                  ---------  ----  ----------  ------  -----------  ----------- ---------- -----------   ------------
Balance,
December 31,
1998............         --    --   6,983,628     698    1,482,685           --         --     (53,371)    (3,391,758)
Issuance of
common stock for
services
(unaudited).....                       83,333       8      411,930
Issuance of
common stock
upon acquisition
of Netranscend..                    1,979,000     198    2,569,068
Issuance of
common stock
upon exercise of
options.........                      175,167      17      340,268
Issuance of
Series A
preferred stock,
net of issuance
costs of
$46,701.........  1,206,000   121                        1,460,678
Conversion of
note payable to
stockholder for
common stock....                      947,009      95       70,931
Issuance of
Series B
preferred stock,
net of issuance
costs of
$741,632........  4,500,000   450                        8,257,918                 432,354
Conversion of
note payable for
common stock....                    4,643,228     464      231,697
Issuance of
Series C
preferred stock,
net of issuance
costs of
$238,441........  4,000,000   400                       14,121,159
Dividend
relative to
beneficial
conversion
feature related
to issuance of
Series C
preferred
stock...........                                                     14,360,000                           (14,360,000)
Issuance of
common stock
upon exercise of
options in
connection with
waiver of
payable to
stockholder
(unaudited).....                      200,000      20       12,400
Issuance of
warrant for
services
(unaudited).....                                                                 2,040,000
Deferred stock
compensation
(unaudited).....                                         9,956,405                          (9,956,405)
Amortization of
deferred stock
compensation
(unaudited).....                                                                             4,413,315
Net loss
(unaudited).....                                                                                          (12,639,784)
                  ---------  ----  ----------  ------  -----------  ----------- ---------- -----------   ------------
Balance,
September 30,
1999............  9,706,000  $971  15,011,365  $1,500  $38,915,139  $14,360,000 $2,472,354 $(5,596,461)  $(30,391,542)
                  =========  ====  ==========  ======  ===========  =========== ========== ===========   ============
<CAPTION>
                     Total
                  ------------
<S>               <C>
Balance,
September 10,
1996
(inception).....  $        --
Issuance of
common stock for
cash and for
services........      152,725
Issuance of
common stock....       80,000
Net loss........     (255,180)
                  ------------
Balance,
December 31,
1996............      (22,455)
Issuance of
common stock....      338,601
Conversion of
payable to
stockholder for
common stock....      232,161
Issuance of
common stock for
services........       11,000
Net loss........   (1,117,366)
                  ------------
Balance,
December 31,
1997............     (558,059)
Repurchase of
common stock for
convertible note
payable.........     (232,161)
Beneficial
conversion
feature of note
payable to
stockholder.....      232,161
Issuance of
common stock....       38,000
Issuance of
common stock for
services........      151,427
Stock-based
compensation....      286,079
Deferred stock
compensation....          --
Amortization of
deferred stock
compensation....      140,019
Net loss........   (2,019,212)
                  ------------
Balance,
December 31,
1998............   (1,961,746)
Issuance of
common stock for
services
(unaudited).....      411,938
Issuance of
common stock
upon acquisition
of Netranscend..    2,569,266
Issuance of
common stock
upon exercise of
options.........      340,285
Issuance of
Series A
preferred stock,
net of issuance
costs of
$46,701.........    1,460,799
Conversion of
note payable to
stockholder for
common stock....       71,026
Issuance of
Series B
preferred stock,
net of issuance
costs of
$741,632........    8,690,722
Conversion of
note payable for
common stock....      232,161
Issuance of
Series C
preferred stock,
net of issuance
costs of
$238,441........   14,121,559
Dividend
relative to
beneficial
conversion
feature related
to issuance of
Series C
preferred
stock...........           --
Issuance of
common stock
upon exercise of
options in
connection with
waiver of
payable to
stockholder
(unaudited).....       12,420
Issuance of
warrant for
services
(unaudited).....    2,040,000
Deferred stock
compensation
(unaudited).....           --
Amortization of
deferred stock
compensation
(unaudited).....    4,413,315
Net loss
(unaudited).....  (12,639,784)
                  ------------
Balance,
September 30,
1999............  $19,761,961
                  ============
</TABLE>

  The accompanying notes are an integral part of these financial statements.

                                      F-5
<PAGE>

                                Mediaplex, Inc.

                            Statements of Cash Flows

<TABLE>
<CAPTION>
                                                  Years Ended             Nine Months Ended
                         September 10, 1996      December 31,               September 30,
                           (inception) to   ------------------------  --------------------------
                         December 31, 1996     1997         1998          1998          1999
                         ------------------ -----------  -----------  ------------  ------------
                                                                      (unaudited)   (unaudited)
<S>                      <C>                <C>          <C>          <C>           <C>
Cash flows from operat-
 ing activities:
 Net loss...............     $(255,180)     $(1,117,366) $(2,019,212) $ (1,116,941) $(12,639,784)
 Adjustments to
  reconcile net loss to
  net cash used in
  operating activities:
 Depreciation and amor-
  tization..............         1,726           20,023       54,810        49,836       766,469
 Write-off of property
  and equipment.........            --               --       18,853            --            --
 Allowance for doubtful
  accounts..............            --           20,211       17,156        20,211     1,207,794
 Stock-based compensa-
  tion expense..........       152,694           11,000      577,525       338,671     6,705,251
 Interest expense re-
  lated to beneficial
  conversion feature of
  note payable to
  stockholder...........            --               --      232,161       232,161            --
 Changes in assets and
  liabilities:
  Accounts receivable...            --          (24,178)    (949,686)     (373,265)   (5,686,969)
  Other assets..........        (1,650)          (3,350)     (22,030)        4,569    (1,176,828)
  Accounts payable......           800          378,322    1,149,477       584,850      (919,947)
  Payables to stock-
   holders..............        35,982          309,621       90,828       (45,522)      (50,000)
  Accrued liabilities...        37,203          112,864      272,110       401,110     4,648,761
  Deferred revenues.....            --          142,400      337,364        57,101     1,078,487
  Other liabilities.....            --               --        1,039        13,650        (1,039)
                             ---------      -----------  -----------  ------------  ------------
   Net cash provided
    (used) in operating
    activities..........       (28,425)        (150,453)    (239,605)      166,431    (6,067,799)
                             ---------      -----------  -----------  ------------  ------------
Cash flows from invest-
 ing activities:
 Purchase of property
  and equipment.........       (24,488)         (69,892)     (78,819)      (43,560)   (2,003,256)
                             ---------      -----------  -----------  ------------  ------------
   Net cash used in in-
    vesting activities..       (24,488)         (69,892)     (78,819)      (43,560)   (2,003,256)
                             ---------      -----------  -----------  ------------  ------------
Cash flows from financ-
 ing activities:
 Net proceeds from issu-
  ance of common stock..        80,031          338,601       38,000        38,000            --
 Net proceeds from issu-
  ance of Series A pre-
  ferred stock..........            --               --           --            --     1,198,170
 Net proceeds from issu-
  ance of Series B pre-
  ferred stock..........            --               --           --            --     8,690,722
 Net proceeds from issu-
  ance of Series C pre-
  ferred stock..........            --               --           --            --    14,212,059
 Proceeds from exercise
  of stock options......            --               --           --            --       340,163
 Payments of capital
  lease obligations.....            --           (3,380)     (24,753)      (23,265)           --
 Proceeds from notes
  payables--stockhold-
  ers...................            --               --      275,000       275,000      (225,000)
 Payment of notes pay-
  able--stockholders....            --               --           --            --            --
 Advance from stockhold-
  er....................            --               --      262,750            --            --
                             ---------      -----------  -----------  ------------  ------------
   Net cash provided by
    financing activi-
    ties................        80,031          335,221      550,997       289,735    24,216,114
                             ---------      -----------  -----------  ------------  ------------
   Net change in cash
    and cash equiva-
    lents...............        27,118          114,876      232,573       412,606    16,145,065
Cash and cash equiva-
 lents at beginning of
 period.................            --           27,118      141,994       141,994       374,567
                             ---------      -----------  -----------  ------------  ------------
Cash and cash equiva-
 lents at end of peri-
 od.....................     $  27,118      $   141,994  $   374,567  $    554,600  $ 16,519,632
                             =========      ===========  ===========  ============  ============
</TABLE>


   The accompanying notes are an integral part of these financial statements.

                                      F-6
<PAGE>

                                Mediaplex, Inc.

                     Supplemental Disclosure of Cash Flows

<TABLE>
<CAPTION>
                          September 10,
                               1996         Years Ended       Nine Months Ended
                          (inception) to   December 31,         September 30,
                           December 31,  ----------------- -----------------------
                               1996        1997     1998      1998        1999
                          -------------- -------- -------- ----------- -----------
                                                           (unaudited) (unaudited)
<S>                       <C>            <C>      <C>      <C>         <C>
Cash paid for interest..      $   --     $  2,572 $  1,804  $  1,773   $    12,976
                              ======     ======== ========  ========   ===========
Noncash financing and
 investing activities:
 Issuance of common
  stock for
  acquisition...........      $   --     $     -- $     --  $     --   $ 2,552,910
                              ======     ======== ========  ========   ===========
 Issuance of note
  payable for
  acquisition...........      $   --     $     -- $     --  $     --   $   430,000
                              ======     ======== ========  ========   ===========
 Conversion of payables
  to stockholders to
  common stock..........      $   --     $232,161 $     --  $     --   $        --
                              ======     ======== ========  ========   ===========
 Conversion of
  stockholders' notes
  payable to common
  stock.................      $   --     $        $     --  $     --   $   303,187
                              ======     ======== ========  ========   ===========
 Repurchase of common
  stock in exchange for
  a note payable........      $   --     $     -- $232,161  $232,161   $        --
                              ======     ======== ========  ========   ===========
 Issuance of note
  payable to stockholder
  for settlement of
  outstanding payable to
  stockholder...........      $   --     $ 64,569 $     --  $     --   $        --
                              ======     ======== ========  ========   ===========
 Issuance of warrant to
  purchase common and
  preferred stock in
  connection with
  completing Series B
  preferred stock
  financing.............      $   --     $     -- $     --  $     --   $   432,354
                              ======     ======== ========  ========   ===========
 Conversion of advance
  from stockholder to
  Series A preferred
  stock.................      $   --     $     -- $     --  $     --   $   262,750
                              ======     ======== ========  ========   ===========
 Conversion of note pay-
  able and accrued in-
  terest to Series C
  preferred stock.......      $   --     $     -- $     --  $     --   $    69,502
                              ======     ======== ========  ========   ===========
 Beneficial conversion
  feature of Series C
  convertible preferred
  stock.................      $   --     $     -- $     --  $     --   $14,360,000
                              ======     ======== ========  ========   ===========
 Exercise of common
  stock options in
  connection with waiver
  of payable to
  stockholder...........      $   --     $     -- $     --  $     --   $    12,420
                              ======     ======== ========  ========   ===========
 Purchase of equipment
  under capital leases..      $   --     $ 37,915 $  3,036  $  3,036   $        --
                              ======     ======== ========  ========   ===========
 Deferred stock
  compensation from
  issuance of options...      $   --     $     -- $193,390  $     --   $ 9,956,405
                              ======     ======== ========  ========   ===========
 Issuance of warrant for
  services..............      $   --     $     -- $     --  $     --   $ 2,040,000
                              ======     ======== ========  ========   ===========
</TABLE>



   The accompanying notes are an integral part of these financial statements.

                                      F-7
<PAGE>

                                Mediaplex, Inc.

                         Notes to Financial Statements

1. Business Activities and Summary of Significant Accounting Policies

Nature of Business

  Mediaplex, Inc. provides technology-based advertising and marketing services
for companies and advertising agencies that seek to optimize their internet
marketing campaigns. The Company's service offerings include planning and
execution of online media and marketing campaigns, proprietary third-party ad
serving to advertisers, and tracking and reporting of an advertiser's return on
investment ("ROI"), including evaluation of online transactions.

Reincorporation

  In August 1999, the Company approved reincorporating in Delaware and changing
its name to Mediaplex, Inc. In connection with the reincorporation, the Company
authorized (i) an increase in the number of authorized shares of common stock
to 150,000,000 and (ii) 10,000,000 shares of undesignated preferred stock. All
share data and stock option plan information has been restated to reflect the
reincorporation. The reincorporation is expected to be completed in 1999.

Netranscend Software, Inc. Acquisition

  On March 25, 1999, the Company acquired Netranscend Software, Inc., a Java-
based business automation solutions software company, for a note payable of
$430,000, due in four annual installments (Note 5) beginning on the first
anniversary of the acquisition, and 1,979,000 shares of the Company's common
stock with an estimated fair value of $1.29 per share. The Company incurred
transaction costs of $68,231.

  The acquisition was accounted for using the purchase method of accounting.
The aggregate purchase price of $2,993,906, together with $15,826 of net
liabilities assumed, has been allocated based on the fair value of the assets
acquired. Goodwill and intangible assets, consisting of proprietary technology,
totaling $3,009,732 are being amortized over three years.

  The following pro forma results of operations reflect the combined results of
the Company and Netranscend Software, Inc. for the fiscal years ended December
31, 1997 and 1998 and have been prepared as though the entities had been
combined as of January 1, 1997 and 1998, respectively. The pro forma results do
not reflect any nonrecurring charges that resulted directly from the
transaction.

<TABLE>
<CAPTION>
                                                        1997         1998
                                                     -----------  -----------
                                                           (unaudited)
   <S>                                               <C>          <C>
   Revenues......................................... $   425,877  $ 3,558,094
   Net loss......................................... $(2,124,951) $(3,032,444)
   Net loss per share--basic and diluted............ $     (0.20) $     (0.30)
   Shares used to compute net loss per share--basic
    and diluted.....................................  10,436,464   10,165,127
</TABLE>

Unaudited Interim Financial Information

  The accompanying balance sheet at September 30, 1999, the accompanying
interim statements of operations and cash flows for the nine months ended
September 30, 1998 and 1999 and the accompanying statement of changes in
stockholders' equity for the nine months ended September 30, 1999 are
unaudited. The unaudited interim financial statements have been prepared on the
same basis as the annual financial statements and, in the opinion of
management, reflect all adjustments, which include only normal recurring
adjustments, necessary to present fairly the Company's results of operations
and cash flows for the nine months ended September 30, 1998 and 1999. The
financial data and other information related to this period that are disclosed
in these notes to consolidated financial statements are unaudited. Results for
the nine months ended September 30, 1999 are not necessarily indicative of
results that may be expected for the full year.

                                      F-8
<PAGE>

                                Mediaplex, Inc.

                   Notes to Financial Statements--(Continued)


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.

Concentration of Credit Risk

  Financial instruments that potentially subject the Company to concentration
of credit risk consist primarily of cash equivalents and accounts receivable.
The Company has cash equivalents and short-term investment policies that
require placement of these funds in financial institutions evaluated as highly
credit-worthy. The Company's credit risk is mitigated by the Company's ongoing
credit evaluation of its customers' financial condition. The Company does not
require collateral or other security to support accounts receivable and
maintains an allowance for doubtful accounts. At December 31, 1997, one
customer accounted for 67% of the outstanding accounts receivable. Four
customers accounted for 76% of the outstanding accounts receivable at December
31, 1998. At September 30, 1999, three customers represented 50% of outstanding
accounts receivable. One, two, four and three customers accounted for 91%, 77%,
80% and 38% of revenues for the years ended December 31, 1997 and 1998, and the
nine months ended September 30, 1998 and 1999, respectively.

Risks and Uncertainties

  The Company is subject to all of the risks inherent in an early stage company
in the Internet advertising industry. These risks include, but are not limited
to, a limited operating history, limited management resources, dependence upon
consumer acceptance of the Internet, Internet-related security risks and the
changing nature of the electronic commerce industry. The Company's operating
results may be materially affected by the foregoing factors.

Fair Value of Financial Instruments

  The Company's financial instruments include cash and cash equivalents,
borrowings and accounts payable, and are carried at cost, which approximates
their fair value due to their short-term maturities.

Cash and Cash Equivalents

  All highly liquid instruments purchased with an original maturity of three
months or less are considered to be cash equivalents.

Property and Equipment

  Property and equipment are stated at cost less accumulated depreciation and
amortization. Maintenance and repairs are charged to operations as incurred.
Depreciation and amortization are based on the straight-line method over the
estimated useful lives of the related assets, which range from three to five
years. When assets are retired or otherwise disposed of, the cost and
accumulated depreciation and amortization are removed from the accounts, and
any resulting gain or loss is reflected in operations in the period realized.

Goodwill and Intangible Assets

  Goodwill and intangible assets consist of the excess of the purchase price
paid over the value of identified intangible and tangible net assets resulting
from the acquisition of Netranscend Software, Inc. Due to the rapid

                                      F-9
<PAGE>

                                Mediaplex, Inc.

                   Notes to Financial Statements--(Continued)

technological changes occurring in the Internet industry, the goodwill and
intangible assets are amortized using the straight-line method over three
years, the period of expected benefit. Valuation of goodwill and intangible
assets is based on forecasted discounted cash flows and is reassessed
periodically. Cash flow forecasts are based on trends of historical performance
and management's estimate of future performance, giving consideration to
existing and anticipated competitive and economic conditions.

Impairment of Long-Lived Assets

  The Company reviews its long-lived assets for impairment whenever events or
changes in circumstances indicate that the carrying amount of an asset may not
be recoverable. Recoverability of assets to be held and used is measured by a
comparison of the carrying amount of an asset to future net cash flows expected
to be generated by the asset. If such assets are considered to be impaired, the
impairment to be recognized is measured by the amount by which the carrying
amount of the assets exceeds the fair value of the assets.

Revenue Recognition

  Revenues are generated primarily from fixed fees for advertising campaign
management services. Advertising revenues are recognized ratably as impressions
are delivered over the period in which the advertisement is displayed, provided
that no significant Company obligations remain at the end of a period and
collection of the resulting receivable is probable. Company obligations
typically includes guarantees of minimum number of "impressions," or times that
an advertisement appears in pages viewed by users of the Company's online
properties. To the extent minimum guaranteed impressions are not met, the
Company defers recognition of the corresponding revenues until the remaining
guaranteed impression levels are achieved.

  Amounts payable to third-party Web sites for providing advertising space are
recorded as cost of revenues in the period the advertising impressions are
delivered.

Deferred Revenues

  Deferred revenues consist of advertising fees received or billed in advance
of delivery of the advertisement.

Research and Development

  Research and development costs are charged to expense as incurred.

Advertising Expenses

  The Company expenses the cost of advertising and promoting its services as
incurred. These costs are included in sales and marketing on the statements of
operations. The Company has not incurred any advertising expenses to date.

Stock-based Compensation

  The Company accounts for stock-based employee compensation arrangements in
accordance with provisions of Accounting Principles Board Opinion ("APB") No.
25, "Accounting for Stock Issued to Employees," and complies with the
disclosure provisions of Statement of Financial Accounting Standards ("SFAS")
No. 123, "Accounting for Stock-Based Compensation." Under APB No. 25,
compensation cost is recognized based on the difference, if any, on the date of
grant between the fair value of the Company's stock and the amount an employee
must pay to acquire the stock.

                                      F-10
<PAGE>

                                Mediaplex, Inc.

                   Notes to Financial Statements--(Continued)


  The Company accounts for non-employee stock-based awards in which goods or
services are the consideration received for the equity instruments issued in
accordance with the provisions of SFAS No. 123 and Emerging Issues Task Force
No. 96-18, "Accounting for Equity Instruments that are Issued to Employees for
Acquiring, or in Conjunction with Selling, Goods or Services."

  The Company amortizes stock-based compensation recorded in connection with
certain stock option grants over the vesting periods of the related options.

Income Taxes

  In accordance with SFAS No. 109, "Accounting for Income Taxes," deferred
income taxes are recognized for the differences between the tax bases of assets
and liabilities and their financial reporting amounts based on enacted tax laws
and statutory tax rates applicable to the periods in which the differences are
expected to affect taxable income. A valuation allowance is recognized for
deferred tax assets when it is more likely than not, based on available
evidence, that some portion or all of the deferred tax asset will not be
realized. Income tax expense or benefit is the tax payable or refundable,
respectively, for the period plus or minus the change during the period in
deferred tax assets and liabilities.

Net Loss Per Share

  Net loss per share is presented in accordance with the provisions of SFAS No.
128, "Earnings per Share," and Staff Accounting Bulletin No. 98. Basic net loss
per share is computed based on the weighted average number of shares of common
stock outstanding, while diluted net loss per share reflects the potential
dilution that would occur if preferred stock had been converted and stock
options and warrants had been exercised. Common equivalent shares from
preferred stock, stock options and warrants have been excluded from the
computation of diluted net loss per share as their effect would be
antidilutive.

Pro Forma Net Loss Per Share (unaudited)

  Pro forma net loss per share for the year ended December 31, 1998 and the
nine months ended September 30, 1999 is computed based on the weighted average
number of common shares outstanding, including the exercise of all outstanding
warrants at September 30, 1999, and the assumed conversion of the Company's
Series A, B and C preferred stock into shares of the Company's common stock
that will be effective upon the closing of the Company's initial public
offering, as if such conversion had occurred on January 1, 1998 or at the date
of original issuance, if later. The resulting pro forma adjustment includes an
increase in the weighted average number of shares used to compute basic and
diluted net loss per share of 0 and 4,206,095 for the year ended December 31,
1998 and the nine months ended September 30, 1999, respectively. The
calculation of pro forma diluted net loss per share excludes common stock
subject to repurchase rights and incremental common shares issuable upon the
exercise of stock options.

Comprehensive Income

  The Company complies with the provisions of SFAS No. 130, "Reporting
Comprehensive Income." SFAS No. 130 establishes standards for reporting
comprehensive income and its components in financial statements. Comprehensive
income, as defined, includes all changes in equity (net assets) during a period
from non-owner sources. To date, the Company has not had any significant
transactions that are required to be reported in comprehensive income.

                                      F-11
<PAGE>

                                Mediaplex, Inc.

                   Notes to Financial Statements--(Continued)


Segment Information

  The Company complies with the provisions of SFAS No. 131, "Disclosures about
Segments of an Enterprise and Related Information." The Company operates in a
single business segment providing advertising campaign management services in
the United States.

2. Recently Issued Accounting Standards

  In June 1998, the FASB issued SFAS No. 133, "Accounting for Derivative
Instruments and Hedging Activities," which defines derivatives, requires that
all derivatives be carried at fair value, and provides for hedge accounting
when certain conditions are met. SFAS No. 133 is effective for the Company in
fiscal 2000. Although the Company has not fully assessed the implications of
SFAS No. 133, the Company does not believe the adoption of this statement will
have a material effect on the Company's financial position, results of
operations or cash flows.

  In March 1998, the Accounting Standards Executive Committee ("ASEC") issued
Statement of Position ("SOP") 98-1, "Accounting for the Costs of Computer
Software Developed or Obtained for Internal Use." SOP 98-1 provides guidance on
when costs related to software developed or obtained for internal use should
the capitalized or expensed. The SOP is effective for transactions entered into
for fiscal years beginning after December 15, 1998. The adoption of this
statement did not have a material effect on the Company's financial position,
results of operations or cash flows.

  In April 1998, the ASEC issued SOP 98-5, "Reporting on the Costs of Start-Up
Activities." SOP 98-5 requires the cost of start-up activities, including
organization costs, to be expensed as incurred. The adoption of this statement
did not have a material effect on the Company's financial position, results of
operations or cash flows.

  In December 1998, the AICPA issued SOP 98-9, "Modification of SOP 97-2,
Software Revenue Recognition, with Respect to Certain Transactions." SOP 98-9
amends SOP 97-2 and SOP 98-4 by extending the deferral of the application of
certain provisions of SOP 97-2 amended by SOP 98-4 through fiscal years
beginning on or before March 15, 1999. All other provisions of SOP 98-9 are
effective for transactions entered into in fiscal years beginning after March
15, 1999. The Company does not anticipate adoption of this statement to have a
material effect on the Company's financial position, results of operations or
cash flows.

3. Balance Sheet Data

  Property and equipment as of December 31, 1997, 1998 and September 30, 1999
are summarized as follows:

<TABLE>
<CAPTION>
                                                December 31,
                                              ------------------  September 30,
                                                1997      1998        1999
                                              --------  --------  -------------
                                                                   (unaudited)
<S>                                           <C>       <C>       <C>
Property and equipment, net:
  Computer equipment and software............ $ 90,056  $161,336   $1,941,606
  Furniture..................................    4,321     5,369      207,077
  Leased equipment...........................   37,915        --           --
  Patents....................................       --        --       21,278
  Less: Accumulated depreciation and
   amortization..............................  (21,746)  (60,784)    (325,631)
                                              --------  --------   ----------
                                              $110,546  $105,921   $1,844,330
                                              ========  ========   ==========
</TABLE>

  Depreciation and amortization expense was $20,023, $54,810, $49,836 and
$264,091 for the years ended December 31, 1997 and 1998 and the nine months
ended September 30, 1998 and 1999, respectively.

                                      F-12
<PAGE>

                                Mediaplex, Inc.

                   Notes to Financial Statements--(Continued)


  Accrued liabilities as of December 31, 1997 and 1998 and September 30, 1999
are summarized as follows:

<TABLE>
<CAPTION>
                                                   December 31,
                                                 ----------------- September 30,
                                                   1997     1998       1999
                                                 -------- -------- -------------
                                                                    (unaudited)
<S>                                              <C>      <C>      <C>
Accrued liabilities:
  Accrued cost of revenues...................... $ 94,440 $293,590  $3,793,511
  Accrued payroll-related costs.................   12,383   24,090     305,132
  Other accrued liabilities.....................   43,244  104,497   1,014,045
                                                 -------- --------  ----------
                                                 $150,067 $422,177  $5,112,688
                                                 ======== ========  ==========
</TABLE>

4. Income Taxes

  The Company has incurred losses from inception through December 31, 1998.
Management believes that, based on its history of losses and other factors, the
weight of available evidence indicates it is more likely than not that the
Company will not be able to realize its deferred tax assets. Thus, a full
valuation reserve has been recorded at December 31, 1997 and 1998. The
Company's net deferred tax asset is comprised as follows:

<TABLE>
<CAPTION>
                                                              December 31,
                                                           --------------------
                                                             1997       1998
                                                           --------  ----------
<S>                                                        <C>       <C>
Net operating loss carryforwards.......................... $445,000   $ 896,000
Deferred liabilities......................................   61,000     205,000
Deferred stock compensation...............................       --          --
Other.....................................................  (24,000)    (44,000)
                                                           --------  ----------
                                                            482,000   1,057,000
Less valuation allowance.................................. (482,000) (1,057,000)
                                                           --------  ----------
 Net deferred tax asset................................... $     --  $       --
                                                           ========  ==========
</TABLE>

  As of December 31, 1998, the Company has net operating loss carryforwards of
approximately $2,083,000 and $2,123,000 for federal and state income tax
purposes, respectively. The carryforwards will begin to expire in 2017 and 2012
for federal and state income tax purposes, respectively. For federal and state
income tax purposes, a portion of the Company's net operating loss may be
subject to certain limitations on annual utilization due to changes in
ownership, as defined by federal and state tax laws. The amount of such
limitations, if any, has not yet been determined.

The components of income tax provision are as follows:

<TABLE>
<CAPTION>
                                                               December 31,
                                                             ------------------
                                                               1997      1998
                                                             --------  --------
<S>                                                          <C>       <C>
Deferred....................................................
 Federal.................................................... $346,000  $445,000
 State......................................................   95,000   130,000
                                                             --------  --------
  Total deferred............................................  441,000   575,000
Change in valuation allowance............................... (441,000) (575,000)
                                                             --------  --------
Total....................................................... $     --  $     --
                                                             ========  ========
</TABLE>

                                      F-13
<PAGE>

                                Mediaplex, Inc.

                   Notes to Financial Statements--(Continued)


The principal items accounting for the difference between income taxes computed
at the U.S. statutory rate and the provision for income taxes are as follows:

<TABLE>
<CAPTION>
                                                   September 10,
                                                       1998       December
                                                    (Inception)      31,
                                                    to December  -------------
                                                     31, 1996    1997    1998
                                                   ------------- -----   -----
<S>                                                <C>           <C>     <C>
U.S. statutory rate...............................      34.0 %    34.0 %  34.0 %
Permanent difference..............................     (20.4)     (0.3)   (9.8)
Adjustment to increase valuation allowance........     (13.6)    (33.7)  (24.2)
                                                       -----     -----   -----
                                                          -- %      -- %    -- %
                                                       =====     =====   =====
</TABLE>

5. Notes Payable to Stockholders

  The Company's notes payable to stockholders consisted of the following:

<TABLE>
<CAPTION>
                                                   December 31,
                                                 ---------------- September 30,
                                                  1997     1998       1999
                                                 ------- -------- -------------
                                                                   (unaudited)
<S>                                              <C>     <C>      <C>
Convertible note payable to stockholder, 6% per
 annum, due July 1999..........................  $64,569 $ 64,569   $     --
Convertible note payable to stockholder, 6% per
 annum, due April 2000.........................       --  232,161         --
Convertible notes payable to stockholder, 6%
 per annum, due August 1999....................       --  150,000         --
Notes payable to stockholder, 6% per annum, due
 August 1999...................................       --  125,000         --
Note payable to stockholder....................       --       --    372,765
                                                 ------- --------   --------
Total notes payable to stockholders............   64,569  571,730    372,765
Less current portion...........................       --  339,569    110,000
                                                 ------- --------   --------
                                                 $64,569 $232,161   $262,765
                                                 ======= ========   ========
</TABLE>

  A law firm affiliated with a stockholder performed legal services for the
Company during 1996 and 1997. In July 1997, the Company issued a convertible
note payable to the law firm for $64,569 for these services. This note bore
interest at a rate of 6% per annum, and had a due date of July 1999. In March
1999, the Company converted the outstanding amount and accrued interest of
$6,458 into 947,009 shares of common stock at $0.075 per share. The law firm
subsequently transferred the shares to the stockholder.

  During 1996 and 1997, a founder of the Company purchased certain assets and
incurred expenses on behalf of the Company (Note 8). In June 1997, $232,161 of
the outstanding amount was converted into 4,643,228 shares of common stock at
$0.05 per share. In April 1998, the Company repurchased the 4,643,228 shares
from the founder at the original conversion price of $0.05 per share with a
convertible promissory note payable. The note bore interest at the rate of 6%
per annum, was due in April 2000, and was convertible into common stock at
$0.05 per share. The Company recorded the difference between the conversion
price of the note and the fair value of the common stock, or the beneficial
conversion feature, on the date the note was issued as additional interest
expense. In March 1999, this outstanding promissory note payable was converted
into 4,643,228 shares of common stock at $0.05 per share.

  In May 1998, the Company entered into two senior subordinated secured
convertible promissory notes and two senior subordinated secured promissory
notes with a stockholder. Under these agreements, the stockholder advanced to
the Company a total of $275,000 bearing interest at the rate of 6% per annum.
The unpaid principal and accrued interest were payable on August 1, 1999, but
could be prepaid without penalty. In the

                                      F-14
<PAGE>

                                Mediaplex, Inc.

                   Notes to Financial Statements--(Continued)

event of any default, as defined in the agreement, the holder could convert the
outstanding amount and accrued interest into preferred stock at the price that
was applicable to preferred stock issued in the most recent round of financing.
At December 31, 1998, the outstanding notes payable balance was $275,000. In
May  1999, the Company paid $225,000 along with the accrued interest to the
stockholder. In August 1999, the holder of the $50,000 note payable converted
the note and the related accrued interest into 19,360 shares of Series C
convertible preferred stock. At September 30, 1999, nothing remained
outstanding.

  In connection with the Netranscend Software, Inc. acquisition in March 1999,
the Company agreed to pay $430,000 as a part of the purchase consideration.
This note is payable over four years, with the first payment of $110,000 due on
the first anniversary, $110,000 due on the second anniversary, $100,000 due on
the third anniversary and $110,000 due on the fourth anniversary. The note
payable has been recorded at $372,765, net of a discount. The discount will be
amortized as interest expense over the four-year term of the note.

  The Company incurred interest expense of $17,015, $10,102 and $12,976 during
1998 and the nine months ended September 30, 1998 and 1999, respectively, in
connection with the notes payable to stockholders.

6. Commitments and Contingencies

Lease Agreements

  The Company leases office space under noncancelable operating lease
agreements that expire in 2002. The terms of the leases provide for rental
payments on a graduated scale. The Company recognizes rent expense on a
straight-line basis over the lease period, and has accrued for rent expense
incurred but not paid.

  Future minimum lease payments under noncancelable operating leases as of
September 30, 1999 are as follows:

<TABLE>
<CAPTION>
      Three Months
      Ended December 31,
      ------------------
      <S>                                                             <C>
        1999........................................................  $   51,775

<CAPTION>
      Year Ended December 31,
      -----------------------
      <S>                                                             <C>
        2000........................................................     327,966
        2001........................................................     338,583
        2002........................................................     332,176
        2003........................................................     148,295
                                                                      ----------
                                                                      $1,198,795
                                                                      ==========
</TABLE>

  Rent expense was $5,366, $41,555, $92,550, $62,954 and $286,812 for the
period ended December 31, 1996, the years ended December 31, 1997 and 1998 and
the nine months ended September 30, 1998 and 1999, respectively.

Severance Payments

  The Company has entered into employment agreements under which the employees
would be entitled to receive severance payments totalling $825,000 if their
employment were terminated under certain conditions.

Legal Proceedings


  From time to time, the Company is subject to legal proceedings and claims in
the ordinary course of business. The Company is not currently aware of any
legal proceedings or claims that it believes will have, individually or in the
aggregate, a material adverse effect on its business, financial condition or
operating results.


                                      F-15
<PAGE>

                                Mediaplex, Inc.

                   Notes to Financial Statements--(Continued)

7. Stockholders' Equity (Deficit)

Convertible Preferred Stock

  The Company is authorized to issue 9,981,000 shares of preferred stock, of
which 1,206,000 shares are designated as Series A preferred stock, 4,775,000
shares are designated as Series B preferred stock and 4,000,000 shares are
designated as Series C preferred stock.

  In August 1999, the Company issued 4,000,000 shares of Series C convertible
preferred stock at a purchase price of $3.59 per share. Such shares are
convertible into shares of common stock on a one-for-one basis. The deemed fair
value of the common stock was based on the low end of the price range for the
anticipated public offering. Consequently, the transaction resulted in a
beneficial conversion feature of $14,360,000. The beneficial conversion feature
has been reflected as a preferred dividend in the statement of operations in
the third quarter of 1999.

  Preferred stock at September 30, 1999 consisted of the following:

<TABLE>
<CAPTION>
                                        Shares                     Cash Proceeds
                                ----------------------                Net of
                                           Issued and  Liquidation   Issuance
Series                          Authorized Outstanding   Amount        Costs
- ------                          ---------- ----------- ----------- -------------
<S>                             <C>        <C>         <C>         <C>
A.............................. 1,206,000   1,206,000  $ 1,507,500  $ 1,460,799
B.............................. 4,775,000   4,500,000    9,000,000    8,258,368
C.............................. 4,000,000   4,000,000   14,360,000   14,121,559
                                ---------   ---------  -----------  -----------
Total.......................... 9,981,000   9,706,000  $24,867,500  $23,840,726
                                =========   =========  ===========  ===========
</TABLE>

  The holders of convertible preferred stock have various rights and
preferences as follows:

 Voting Rights

  Each holder of Series A, Series B and Series C preferred stock is entitled to
the number of votes equal to the number of shares of common stock into which
the shares of preferred stock held by the holder can be converted. As of
September 30, 1999, all preferred stock converts on a one-for-one basis into
common stock. Preferred stockholders can vote on all matters on which common
stockholders are entitled to vote.

 Dividends

  Holders of Series A, Series B and Series C preferred stock are entitled to
noncumulative dividends at the rate of $0.10 per share, $0.16 per share and
$0.29 per share per annum, respectively, before any dividend is paid on common
stock. No dividends on preferred stock or common stock have been declared by
the Board of Directors from inception through September 30, 1999.

 Liquidation

  In the event of (i) any liquidation, dissolution or winding up of the
Company, either voluntary or involuntary, or (ii) merger or consolidation of
the Company with or into another corporation, the holders of Series A, Series B
and Series C preferred stock are first entitled to receive, in preference to
the holders of common stock, an amount of $1.25, $2.00 and $3.59, respectively,
per share plus all accrued but unpaid dividends. If assets and funds are
insufficient for such distribution, the available funds will be distributed
ratably among the holders of Series A, Series B and Series C preferred stock in
proportion to the preferential amount each holder would have otherwise been
entitled to receive. After such distribution, any remaining funds will be
distributed ratably among the holders of common stock.

                                      F-16
<PAGE>

                                Mediaplex, Inc.

                   Notes to Financial Statements--(Continued)


 Conversion Rights

  Each share of Series A, Series B and Series C preferred stock is convertible
into common shares, at the option of the holder, according to a conversion
ratio, subject to adjustment for dilution. Each share of preferred stock will
automatically be converted into common stock, at the then applicable conversion
rate, (i) in the event of the closing of an underwritten public offering of the
Company's securities in which the aggregate gross proceeds to the Company
exceeds $10,000,000 and an offering price per share exceeds $5.00, or (ii) when
the Company obtains the consent of a majority of the outstanding shares of
preferred stock.

  At September 30, 1999, the Company had reserved 1,206,000 shares, 4,775,000
shares and 4,000,000 shares of common stock for conversion of its Series A,
Series B and Series C convertible preferred stock, respectively.

Common Stock

  The Company is authorized to issue 40,000,000 shares of common stock. In July
1999, the Company amended its certificate of incorporation to increase the
number of authorized shares of common stock to 75,000,000 shares.

  The Company recognizes stock-based compensation upon the issuance of common
stock for less than the deemed fair market value and upon the issuance of
common stock in exchange for services. Accordingly, the Company recorded stock-
based compensation of $152,694, $11,000, $151,427, $151,427 and $251,938 for
the period from September 10, 1996 (inception) to December 31, 1996, the years
ended December 31, 1997 and 1998 and the nine months ended September 30, 1998
and 1999, respectively.

Warrants

  In January 1999, the Company issued a warrant to an employee to purchase
500,000 shares of common stock at $0.50 per share. The warrant becomes
exercisable only upon completion of certain milestones that were primarily
related to achievement of certain levels of earned revenues.

  As of September 30, 1999, all milestones were completed and the warrant to
purchase 500,000 shares became exercisable. Accordingly, the Company recorded
compensation expense in the amount of $2,040,000 based on the difference
between the exercise price and the fair value of the Company's common stock on
the date the milestones were met.

  In June 1999, in connection with services provided related to the issuance of
Series B preferred stock, the Company granted warrants to two non-employees,
exercisable for 275,000 shares of Series B convertible preferred stock and
100,000 shares of common stock at exercise prices of $2.00 per share and $0.50
per share, respectively. The warrants are exercisable by the holder at any time
until June 2002. The holder of the warrant is not entitled to any voting
rights. The fair value of the warrants calculated using Black-Scholes model was
$432,354 and has been included in the offering costs of the Series B
convertible preferred stock.

1997 Stock Plan

  The Company's 1997 Stock Plan provides for the granting to employees of
incentive stock options within the meaning of Section 422 of the Internal
Revenue Code and for the granting to employees and consultants of nonstatutory
stock options and stock purchase rights.

  In November 1998, the Company granted options to purchase 505,667 shares of
common stock with exercise prices ranging from $0.05 to $0.30 to both former
and current employees for services previously

                                      F-17
<PAGE>

                                Mediaplex, Inc.

                   Notes to Financial Statements--(Continued)

rendered under the 1997 Stock Plan. The options granted to former employees
were immediately exercisable until February 1999. For those options granted to
current employees, the Company recorded $193,390 in deferred stock compensation
for the difference between the exercise price and the assumed fair value of the
common stock. For the year ended December 31, 1998, the Company recorded stock
compensation expense of $140,019.

  The Company recorded the fair value for the options granted to former
employees as stock-based compensation expense of $286,079 in 1998. The fair
value of the options granted to the former employees was determined using a
Black-Scholes option-pricing model using a weighted average risk-free rate of
4.65%, weighted average expected life of three months and price volatility of
103%. No dividend yield was assumed as the Company has not paid dividends and
has no plans to do so.

1999 Stock Plan

  In February 1999, the Company adopted the 1999 Stock Plan (the "1999 Plan").
Options granted under the 1999 Plan may be either incentive stock options
("ISOs") or nonstatutory stock options ("NSOs"). ISOs may be granted only to
Company employees. NSOs may be granted to Company employees, directors and
consultants. The Company has reserved 9,000,000 shares of common stock for
issuance under the 1999 Plan. The 1999 Plan was amended in August 1999, raising
the number of shares reserved for issuance to 12,000,000.

  In the case of ISOs granted to an employee who, at the time of the option was
granted, owns stock representing more than 10% of the voting power of all
classes of stock, the term of the option cannot exceed five years. The exercise
price of an ISO or NSO may not be less than 100% or 85%, respectively, of the
estimated fair value of the underlying stock on the date of grant and the
exercise price of an ISO or NSO granted to a 10% shareholder may not be less
than 100% of the estimated fair value of the underlying stock on the date of
grant. Options generally become exercisable in equal increments over a four-
year vesting period and expire at the end of ten years from the date of grant,
or sooner if terminated by the Board of Directors.

  The following table summarizes option activity through September 30, 1999:

<TABLE>
<CAPTION>
                                                    Options Outstanding
                           Shares    ---------------------------------------------------
                         Available   Number of   Exercise   Aggregate   Weighted Average
                         for Grants   Shares       Price      Price      Exercise Price
                         ----------  ---------  ----------- ----------  ----------------
<S>                      <C>         <C>        <C>         <C>         <C>
Share authorized under
 the 1997 Plan              505,667
Granted.................   (505,667)   505,667  $0.05-$0.30 $   91,935       $0.18
Cancelled...............         --         --           --         --          --
Exercised...............         --   (262,667) $0.05-$0.30    (19,035)      $0.07
                         ----------  ---------              ----------
Balance, December 31,
 1998...................         --    243,000        $0.30     72,900       $0.30
Shares authorized under
 the 1999 Plan.......... 12,000,000         --
Granted................. (9,173,398) 9,173,398  $0.50-$6.50  7,630,873       $0.83
Cancelled...............     16,700    (16,700)       $0.50     (8,350)      $0.50
Exercised...............         --   (112,500) $0.50-$3.25   (337,500)      $3.00
                         ----------  ---------              ----------
Balance, September 30,
 1999...................  2,843,302  9,287,198  $0.50-$3.25 $7,285,023       $0.78
                         ==========  =========              ==========
</TABLE>

                                      F-18
<PAGE>

                                Mediaplex, Inc.

                   Notes to Financial Statements--(Continued)


  The following table summarizes information for stock options outstanding at
September 30, 1999:

<TABLE>
<CAPTION>
                                                                       Options
                            Options Outstanding                      Exercisable
        ------------------------------------------------------------------------
                                                    Weighted Average
                                                       Remaining
        Exercise                          Number    Contractual Life   Number
          Price                         Outstanding     (Years)      Exercisable
        --------                        ----------- ---------------- -----------
       <S>                              <C>         <C>              <C>
        $0.30..........................    243,000        7.8           130,166
        $0.50..........................  7,969,660        9.2         4,842,872
        $1.80..........................    241,038        9.5             1,265
        $3.25..........................    760,700        9.7            50,000
        $6.50..........................     72,800        9.9               --
                                         ---------                    ---------
                                         9,287,198                    5,024,303
                                         =========                    =========
</TABLE>

  In connection with the stock option grants made during the nine months ended
September 30, 1999, the Company recorded deferred stock compensation of
$9,956,405, which will be amortized over the vesting periods of the related
stock options through 2003. For the nine months ended September 30, 1999, the
Company recorded stock compensation expense of $4,413,315 in connection with
stock option grants.

  The Company recorded the fair value for the options granted to non-employees
as stock-based compensation expense of $984,019 for nine months ended September
30, 1999. The fair value of the options granted to the non-employees were
determined using Black-Scholes option-pricing model using a weighted average
risk-free rate of 4.87%, a weighted average expected life of 2.2 years and
price volatility of 75%. No dividend yield was assumed as the Company has not
paid dividends and has no plans to do so.

  Under SFAS No. 123, the Company is required to calculate the pro forma fair
market value of options granted and report the impact that would result from
recording the compensation expense. The fair value of option grants has been
estimated on the date of grant using the Black-Scholes option-pricing model
using a weighted average risk-free interest rate of 4.82% and a weighted
average expected life of 3.2 years. No price volatility was assumed because the
Company's equity securities were not traded publicly. No dividend yield was
assumed as the Company has not paid dividends and has no plans to do so.

  The weighted average expected life was calculated based on the vesting period
and the expected life at the date of grant. The risk-free interest rate was
calculated based on rates prevailing during the grant periods and expected
lives of options at the date of grants.

  The weighted average fair values of options granted to employees for the year
ended December 31, 1998 was $1.06.

  Had compensation expenses for option grants to employees been determined
under SFAS No. 123 the Company's net loss would have been as follows:

<TABLE>
<CAPTION>
                                       September 10,
                                           1996       Years Ended December
                                        (inception)            31,
                                        to December  ------------------------
                                         31, 1996       1997         1998
                                       ------------- -----------  -----------
<S>                                    <C>           <C>          <C>
Net loss--as reported.................   $(255,180)  $(1,117,366) $(2,019,212)
Net loss--pro forma...................   $(255,180)  $(1,117,366) $(2,019,212)
Net loss per share--basic and diluted
 as reported..........................   $   (0.07)  $     (0.13) $     (0.25)
Net loss per share--basic and diluted
 pro forma............................   $   (0.07)  $     (0.13) $     (0.25)
</TABLE>

                                      F-19
<PAGE>

                                Mediaplex, Inc.

                   Notes to Financial Statements--(Continued)


  The pro forma net loss disclosures made above are not necessarily
representative of the effects on pro forma net income (loss) for future years
as options typically vest over several years and additional option grants are
expected to be made in future years.

8. Related Party Transactions

  Related party balances consist of the following:

<TABLE>
<CAPTION>
                                                    December 31,
                                                  ---------------- September 30,
                                                   1997     1998       1999
                                                  ------- -------- -------------
                                                                    (unaudited)
<S>                                               <C>     <C>      <C>
Payables to stockholders......................... $19,203 $ 71,781    $71,781
Payables to founders.............................  29,670   67,920      5,500
                                                  ------- --------    -------
    Total payables to stockholders............... $48,873 $139,701    $77,281
                                                  ======= ========    =======
</TABLE>

  The Company incurred expenses of $21,547, $66,546 and $196,611 for the period
from September 10 (inception) to December 31, 1996 and the years ended December
31, 1997 and 1998, respectively, in connection with legal and consulting
services performed by a law firm affiliated with a stockholder.

  During 1996 and 1997, founders of the Company purchased certain assets and
incurred expenses on behalf of the Company for a total of $274,661. In June
1997, $232,161 of the outstanding amount was converted into common stock (see
Note 5). During 1997 and 1998, $12,830 and $11,750 was paid back to the
founders, respectively. In 1998, a founder advanced the Company $50,000.

  In January 1999, the Company converted $12,420 of the payables to founders
into 200,000 shares of common stock in connection with the founder's exercise
of stock options.

  In May 1998, the Company entered into a sublease agreement, on a month-to-
month basis, for office space with a stockholder, who was the original tenant
of the office space. The Company paid $41,000, $28,000 and $70,800 during the
year ended December 31, 1998 and the nine months ended September 30, 1998 and
1999, respectively, to the stockholder.

  In June 1999, the Company entered into an agreement with a former employee
and stockholder, under which the stockholder will receive commissions on the
net proceeds (defined as gross revenue minus associated costs) generated from
certain customers. The agreement expires in July 2000.

9. Employee Benefit Plan

  The Company maintains a retirement and deferred savings plan for its
employees (the "401(k) Plan") that is intended to qualify as a tax-qualified
plan under the Internal Revenue Code. The 401(k) Plan provides that each
participant may contribute up to 15% of his or her pre-tax gross compensation
(up to a statutory limit). All amounts contributed by participants and earnings
on these contributions are fully vested at all times. To date, the Company has
not made discretionary contributions under the 401(k) Plan.

10. Employee Stock Purchase Plan

  In August 1999, the Board of Directors adopted the 1999 Employee Stock
Purchase Plan (the "Purchase Plan") effective on the date of the Company's
initial public offering. The Company has reserved 400,000 shares for issuance
thereunder. Employees generally will be eligible to participate in the Purchase
Plan if they

                                      F-20
<PAGE>

                                Mediaplex, Inc.

                   Notes to Financial Statements--(Continued)

are customarily employed by the Company for more than 20 hours per week and
more than five months in a calendar year and are not 5% or greater
stockholders. Under the Purchase Plan, eligible employees may select a rate of
payroll deduction up to 10% of their compensation subject to certain maximum
purchase limitations. The Purchase Plan will be implemented in a series of
overlapping twenty-four month offering periods beginning on the effective date
of the Company's initial public offering. Subsequent offering periods will
begin on the first trading day on or after May 1 and November 1 of each year.
Purchases will occur on each April 30 and October 31 (the "purchase dates")
during each participation period. Under the Purchase Plan, eligible employees
will be granted an option to purchase shares of common stock at a purchase
price equal to 85% of the fair market value per share of common stock on either
the start date of the offering period or the end date of the offering period,
whichever is less. If the fair market value of the common stock at the end of
the purchase period is lower than the fair market value on the start date of
that offering period, then all participants in that offering period will be
automatically withdrawn from such offering period and re-enrolled in the
offering period immediately following.

  The Company amended the 1999 Stock Plan in August 1999, increasing the number
of shares reserved for issuance to 12,000,000.

11. Pro Forma Stockholders' Equity (unaudited)

  Pro forma stockholders' equity is computed to include the automatic
conversion of the pro forma outstanding shares of Series A, Series B, and
Series C preferred stock into 1,206,000, 4,500,000 and 4,000,000 shares,
respectively, of common stock.

  At September 30, 1999, the pro forma effects of these transactions are as
follows:

<TABLE>
<CAPTION>
                                                                 Pro Forma
                                                           Stockholders' Equity
                                        September 30, 1999 At September 30, 1999
                                        ------------------ ---------------------
<S>                                     <C>                <C>
Preferred stock........................    $       971          $        --
Common stock...........................          1,500                2,471
Additional paid-in capital.............     38,915,139           38,915,139
Beneficial conversion feature..........     14,360,000           14,360,000
Warrants...............................      2,472,354            2,472,354
Deferred stock compensation............     (5,596,461)          (5,596,461)
Accumulated deficit....................    (30,391,542)         (30,391,542)
                                           -----------          -----------
  Total stockholders' equity...........    $19,761,961          $19,761,961
                                           ===========          ===========
</TABLE>

                                      F-21
<PAGE>

                                Mediaplex, Inc.

                        Pro Forma Financial Information

                                    Overview

  On March 25, 1999, the Company acquired Netranscend Software, Inc.
("Netranscend"), a Java-based business automation solution software company.
The acquisition was accounted for using the purchase method of accounting and,
accordingly, the purchase price was allocated to the tangible and intangible
assets acquired and liabilities assumed on the basis of their fair values on
the acquisition date.

  The aggregate purchase price of $2,993,906 consisted of a note payable of
$430,000, due in four annual installments beginning on the first anniversary of
the acquisition, 1,979,000 shares of the Company's common stock with an
estimated fair value of $2,552,910, acquisition-related expenses of $68,231 for
miscellaneous transaction fees and $15,826 of net liabilities assumed. Of the
total purchase price, $3,009,732 was allocated to goodwill and intangible
assets, consisting of proprietary technology. The acquired goodwill and
intangible assets will be amortized over their estimated useful lives of three
years.

  The following unaudited pro forma consolidated statement of operations gives
effect to this acquisition as if it had occurred on January 1, 1998, by
consolidating the results of operations of Netranscend Software, Inc. for the
year ended December 31, 1998 and the period from January 1, 1999 to March 25,
1999, with the results of operations of the Company for the year ended
December 31, 1998 and the nine months ended September 30, 1999, respectively.

  The unaudited pro forma consolidated statement of operations is not
necessarily indicative of the operating results that would have been achieved
had the transactions been effected as of January 1, 1998 and should not be
construed as being representative of future operating results.

  The historical financial statements of the Company and Netranscend are
included elsewhere in this Prospectus and the unaudited pro forma consolidated
financial information presented herein should be read in conjunction with those
financial statements and related notes.

                                      F-22
<PAGE>

                                Mediaplex, Inc.

                       Pro Forma Statement of Operations
                                  (unaudited)

<TABLE>
<CAPTION>
                                    Year Ended December 31, 1998
                           ---------------------------------------------------
                            Mediaplex   Netranscend Adjustments     Pro Forma
                           -----------  ----------- -----------    -----------
<S>                        <C>          <C>         <C>            <C>
Revenues.................. $ 3,588,094    $    --   $        --    $ 3,588,094
Cost of revenues..........   2,770,567         --            --      2,770,567
                           -----------    -------   -----------    -----------
    Gross profit..........     817,527         --            --        817,527
                           -----------    -------   -----------    -----------

Operating expenses:
  Sales and marketing.....     819,641         --            --        819,641
  Research and
   development............     555,736      1,717            --        557,453
  General and
   administrative.........     636,651      8,271            --        644,922
  Stock-based
   compensation...........     577,525         --            --        577,525
  Amortization of goodwill
   and intangibles........          --         --     1,003,244(A)   1,003,244
                           -----------    -------   -----------    -----------
    Total operating
     expenses.............   2,589,553      9,988     1,003,244      3,602,785
                           -----------    -------   -----------    -----------
    Loss from operations..  (1,772,026)    (9,988)   (1,003,244)    (2,785,258)
Interest expense, net.....    (247,186)        --            --       (247,186)
                           -----------    -------   -----------    -----------
    Net loss.............. $(2,019,212)   $(9,988)  $(1,003,244)   $(3,032,444)
                           ===========    =======   ===========    ===========
Net loss per share--basic
 and diluted(B)...........                                         $     (0.30)
                                                                   ===========
Weighted average shares
 outstanding(B)...........                                          10,165,127
                                                                   ===========
</TABLE>



     See accompanying Notes to Pro Forma Consolidated Financial Information

                                      F-23
<PAGE>

                                Mediaplex, Inc.

                       Pro Forma Statement of Operations
                                  (unaudited)

<TABLE>
<CAPTION>
                                Nine Months Ended September 30, 1999
                          -----------------------------------------------------
                           Mediaplex    Netranscend Adjustments     Pro Forma
                          ------------  ----------- -----------    ------------
<S>                       <C>           <C>         <C>            <C>
Revenues................  $ 13,940,808     $  --     $      --     $ 13,940,808
Cost of revenues........    10,948,571        --            --       10,948,571
                          ------------     -----     ---------     ------------
    Gross profit........     2,992,237        --            --        2,992,237
                          ------------     -----     ---------     ------------

Operating expenses:
  Sales and marketing...     3,523,109        --            --        3,523,109
  Research and
   development..........     2,203,039       408            --        2,203,447
  General and
   administrative.......     2,885,701       156            --        2,885,857
  Stock-based
   compensation.........     6,705,252        --            --        6,705,252
  Amortization of
   goodwill and
   intangibles..........       502,378        --       250,055 (A)      752,433
                          ------------     -----     ---------     ------------
    Total operating
     expenses...........    15,819,479       564       250,055       16,070,098
                          ------------     -----     ---------     ------------
    Loss from
     operations.........   (12,827,242)     (564)     (250,055)     (13,077,861)
Interest income, net....       187,458        --            --          187,458
                          ------------     -----     ---------     ------------
    Net loss............   (12,639,784)     (564)     (250,055)     (12,890,403)
Beneficial conversion
 feature of Series C
 convertible preferred
 stock..................    14,360,000        --            --       14,360,000
                          ------------     -----     ---------     ------------
Net loss attributable to
 common shareholders....  $(26,999,784)    $(564)    $(250,055)    $(27,250,403)
                          ============     =====     =========     ============
Net loss per share--
 basic and diluted(B)...                                           $      (1.99)
                                                                   ============
Weighted average shares
 outstanding(B).........                                             13,661,604
                                                                   ============
</TABLE>



     See accompanying Notes to Pro Forma Consolidated Financial Information

                                      F-24
<PAGE>

                                Mediaplex, Inc.

                    Notes to Pro Forma Financial Information
                                  (unaudited)

  The following adjustments were applied to the Company's historical financial
statements and those of Netranscend Software, Inc. to arrive at the pro forma
consolidated financial information.

   (A) To record amortization of goodwill and purchased proprietary
       technology over the estimated period of benefit of three years.

   (B) Pro forma basic and diluted net loss per share for the year ended
       December 31, 1998 and the nine months ended September 30, 1999, were
       computed using the weighted average number of common shares
       outstanding. Differences between historical weighted average shares
       outstanding and pro forma weighted average shares outstanding used to
       compute net loss per share result from the inclusion of shares issued
       in conjunction with the acquisition as if those shares were
       outstanding from January 1, 1998.

                                      F-25
<PAGE>

                       Report of Independent Accountants

To the Board of Directors and Shareholders of
Netranscend Software, Inc.:

  In our opinion, the accompanying balance sheets and the related statements of
operations, of shareholders' equity (deficit) and of cash flows present fairly,
in all material respects, the financial position of Netranscend Software, Inc.
(a development stage company) (the "Company") at December 31, 1997 and 1998 and
the results of its operations and its cash flows for the years ended December
31, 1997 and 1998, and the period from November 27, 1996 (inception) through
December 31, 1998 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.

/s/ PricewaterhouseCoopers LLP

San Francisco, California
July 23, 1999

                                      F-26
<PAGE>

                           Netranscend Software, Inc.
                         (a development stage company)

                                 Balance Sheets

<TABLE>
<CAPTION>
                                                               December 31,
                                                             -----------------
                                                              1997      1998
                                                             -------  --------
<S>                                                          <C>      <C>
                           Assets
Current assets:
  Cash and cash equivalents................................. $    --  $    530
  Prepaid expenses..........................................     114        78
                                                             -------  --------
    Total current assets....................................     114       608
Property and equipment, net.................................   3,149     1,746
                                                             -------  --------
    Total assets............................................ $ 3,263  $  2,354
                                                             =======  ========
       Liabilities and Shareholders' Equity (Deficit)
Current liabilities:
  Payable due to shareholder................................ $ 6,126  $ 16,356
  Accrued liabilities.......................................   1,171        --
                                                             -------  --------
    Total current liabilities...............................   7,297    16,356
                                                             -------  --------
Shareholders' equity (deficit):
  Common stock: No par value; 10,000,000 shares authorized;
   3,000,000 shares issued and outstanding at December 31,
   1997 and 1998............................................   3,030     3,030
  Deferred stock compensation...............................     (30)      (10)
  Deficit accumulated during the development stage..........  (7,034)  (17,022)
                                                             -------  --------
    Total shareholders' equity (deficit)....................  (4,034)  (14,002)
                                                             -------  --------
    Total liabilities and shareholders' equity (deficit).... $ 3,263  $  2,354
                                                             =======  ========
</TABLE>



   The accompanying notes are an integral part of these financial statements.

                                      F-27
<PAGE>

                           Netranscend Software, Inc.
                         (a development stage company)

                            Statements of Operations

<TABLE>
<CAPTION>
                                                                    Period from
                                                                    November 27,
                                                                        1996
                                                    Year Ended      (inception)
                                                   December 31,       through
                                                  ----------------  December 31,
                                                   1997     1998        1998
                                                  -------  -------  ------------
<S>                                               <C>      <C>      <C>
Operating expenses:
  Research and development....................... $ 1,405  $ 1,717    $  3,219
  Selling, general and administrative............   2,936    8,271      13,803
                                                  -------  -------    --------
    Total operating expenses.....................   4,341    9,988      17,022
                                                  -------  -------    --------
    Net loss..................................... $(4,341) $(9,988)   $(17,022)
                                                  =======  =======    ========
</TABLE>



   The accompanying notes are an integral part of these financial statements.

                                      F-28
<PAGE>

                           Netranscend Software, Inc.
                         (a development stage company)

                  Statements of Shareholders' Equity (Deficit)

<TABLE>
<CAPTION>
                                                          Deficit
                                                        Accumulated     Total
                            Common Stock     Deferred   during the  Shareholders'
                          ----------------    Stock     Development    Equity
                           Shares   Amount Compensation    Stage      (Deficit)
                          --------- ------ ------------ ----------- -------------
<S>                       <C>       <C>    <C>          <C>         <C>
Balance at January 1,
 1997...................  3,000,000 $3,000     $ --      $ (2,693)    $    307
Deferred stock
 compensation...........         --     30      (30)           --           --
Net loss ...............         --     --       --        (4,341)      (4,341)
                          --------- ------     ----      --------     --------
Balance at December 31,
 1997...................  3,000,000  3,030      (30)       (7,034)      (4,034)
Amortization of deferred
 stock compensation.....         --     --       20            --           20
Net loss................         --     --       --        (9,988)      (9,988)
                          --------- ------     ----      --------     --------
Balance at December 31,
 1998...................  3,000,000 $3,030     $(10)     $(17,022)    $(14,002)
                          ========= ======     ====      ========     ========
</TABLE>



   The accompanying notes are an integral part of these financial statements.

                                      F-29
<PAGE>

                           Netranscend Software, Inc.
                         (a development stage company)

                            Statements of Cash Flows

<TABLE>
<CAPTION>
                                                                   Period from
                                                                   November 27,
                                                                       1996
                                                   Year Ended      (inception)
                                                  December 31,       through
                                                 ----------------  December 31,
                                                  1997     1998        1998
                                                 -------  -------  ------------
                                                                   (unaudited)
<S>                                              <C>      <C>      <C>
Cash flows from operating activities:
 Net loss....................................... $(4,341) $(9,988)   $(17,022)
 Adjustments to reconcile net loss to net cash
  used in operating activities:
  Depreciation and amortization.................   1,404    1,618       3,119
  Stock compensation expense....................      --       20          20
  Changes in current assets and liabilities:
    Prepaid expenses............................    (114)      36         (78)
    Accrued liabilities.........................   1,171   (1,171)         --
                                                 -------  -------    --------
      Net cash used in operating activities.....  (1,880)  (9,485)    (13,961)
                                                 -------  -------    --------
Cash flows from investing activities:
 Purchase of property and equipment.............  (1,174)    (215)     (4,865)
                                                 -------  -------    --------
      Net cash used in investing activities.....  (1,174)    (215)     (4,865)
                                                 -------  -------    --------
Cash flows from financing activities:
 Proceeds from issuance of common stock.........      --       --       3,000
 Proceeds from payables due to shareholder......   3,054   10,230      16,356
                                                 -------  -------    --------
      Net cash provided by financing
       activities...............................   3,054   10,230      19,356
                                                 -------  -------    --------
Net increase in cash and cash equivalents.......      --      530         530
Cash and cash equivalents at beginning of
 period.........................................      --       --          --
                                                 -------  -------    --------
Cash and cash equivalents at end of period...... $    --  $   530    $    530
                                                 =======  =======    ========
Supplemental disclosure of cash flow
 information:
 Deferred stock compensation from issuance of
  common stock.................................. $    30  $    --    $     30
                                                 =======  =======    ========
</TABLE>

   The accompanying notes are an integral part of these financial statements.

                                      F-30
<PAGE>

                           Netranscend Software, Inc.
                         (a development stage company)

                         Notes to Financial Statements

1. Nature of Business

  Netranscend Software, Inc. (the "Company") was incorporated on November 27,
1996 as a California corporation. The Company provides Java-based business
automation solutions on the Internet and for intranets.

2. Summary of Significant Accounting Policies

Basis of presentation

  The Company has had limited operations to date, and its activities have
consisted primarily of developing products and recruiting personnel.
Accordingly, the Company is considered to be in the development stage at
December 31, 1998, as defined in Statement of Financial Accounting Standards
("SFAS") No. 7, "Accounting and Reporting by Development Stage Enterprises."

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
reported amounts of revenues and expenses during the reporting period. Actual
results could differ from those estimates.

Cash and cash equivalents

  The Company considers all highly liquid investments purchased with an
original maturity of three months or less to be cash equivalents.

Property and equipment

  Property and equipment are stated at cost and depreciated on the straight-
line basis over the estimated useful lives of the asset, which is generally
three years. Upon sale or disposal, the Company removes the asset and
accumulated depreciation from its records and recognizes the related gain or
loss in results of operations.

Research and development costs

  The costs of establishing the technological feasibility of the Company's
software products or product enhancements are expensed as research and
development costs when incurred. The costs incurred subsequent to the
establishment of technological feasibility and prior to a product's general
release will be capitalized. All costs have been expensed to date.

Stock-based compensation

  The Company accounts for stock-based employee compensation arrangements in
accordance with provisions of APB No. 25, "Accounting for Stock Issued to
Employees," and complies with the disclosure provisions of SFAS No. 123,
"Accounting for Stock-Based Compensation." Under APB No. 25, compensation cost
is recognized based on the difference, if any, on the date of grant between the
fair value of the Company's stock and the amount an employee must pay to
acquire the stock.

                                      F-31
<PAGE>

                           Netranscend Software, Inc.
                         (a development stage company)

                   Notes to Financial Statements--(Continued)


  The Company accounts for non-employee stock-based awards in which goods or
services are the consideration received for the equity instruments issued based
on the fair value of the consideration received or the fair value of the equity
instruments issued, whichever is more reliably measurable.

Comprehensive Income

  The Company complies with the provisions of SFAS No. 130, "Reporting
Comprehensive Income." SFAS No. 130 establishes standards for reporting
comprehensive income and its components in financial statements. Comprehensive
income, as defined, includes all changes in equity (net assets) during a period
from non-owner sources. The Company has not had any significant transactions
that are required to be reported in comprehensive income.

Income Taxes

  Deferred tax assets and liabilities are determined based on the difference
between the financial statements and tax bases of assets and liabilities using
enacted tax rates in effect for the year in which the differences are expected
to affect taxable income. Valuation allowances are established when necessary
to reduce deferred tax assets to the amounts expected to be realized.

Concentration of Credit Risk

  Financial instruments which potentially subject the Company to concentration
of credit risk consist principally of cash and cash equivalents. The Company
deposits its cash and cash equivalents with a single major financial
institution, which deposits may exceed federal deposit insurance limits.

3. Related Party Transactions

  During the period from November 27, 1996 (inception) to December 31, 1998,
the sole shareholder purchased certain assets and incurred expenses on behalf
of the Company. The Company recorded such amounts due to the shareholder as an
interest-free loan. The amounts due to the shareholder at December 31, 1997 and
1998 were $6,126 and $16,356, respectively.

4. Property and Equipment

  Property and equipment as of December 31, 1997 and 1998 is summarized as
follows:

<TABLE>
<CAPTION>
                                                                 December 31,
                                                                 --------------
                                                                  1997    1998
                                                                 ------  ------
   <S>                                                           <C>     <C>
   Property and equipment, net:
     Computer equipment and software............................ $4,651  $4,866
     Less: Accumulated depreciation and amortization............ (1,502) (3,120)
                                                                 ------  ------
                                                                 $3,149  $1,746
                                                                 ======  ======
</TABLE>

                                      F-32
<PAGE>

                           Netranscend Software, Inc.
                         (a development stage company)

                   Notes to Financial Statements--(Continued)


5. Income Taxes

  During the period from November 27, 1996 (inception) through December 31,
1998, no income tax provision or benefit was recognized due to net operating
losses incurred during the periods for which a full valuation allowance was
recorded.

  The difference between the income tax benefit at the federal statutory rate
of 34% and the Company's effective tax rate is due to the recording of the
valuation allowance.

6. Shareholders' Equity

Common stock

  The Company is authorized to issue 10,000,000 shares of common stock. In
November 1996, the Company issued 3,000,000 shares of common stock to the sole
shareholder in exchange for a capital contribution made by the shareholder. At
December 31, 1998, a total of 3,000,000 shares of common stock was issued and
outstanding.

Stock option plan

  The Company did not have a formal stock option plan. However, during 1997,
the Company issued nonstatutory stock options to three non-employees. The
Company did not reserve any specific number of shares of common stock for
issuance of the stock options. The options generally become exercisable in
equal increments over a eighteen-month vesting period and expire at the end of
five years from the date of grant or sooner if terminated by the Board of
Directors.

  In connection with the stock options grants, the Company recorded a deferred
stock compensation of $30, which will be amortized over the vesting period
through February 1999.

  The following table summarizes option activity through December 31, 1998:

<TABLE>
<CAPTION>
                                                        Options Outstanding
                                                    ----------------------------
                                                    Number of Exercise Aggregate
                                                     Shares    Price     Price
                                                    --------- -------- ---------
   <S>                                              <C>       <C>      <C>
   Shares:
     Granted.......................................  59,000    $0.002    $118
     Cancelled.....................................      --        --      --
     Exercised.....................................      --        --      --
                                                     ------    ------    ----
   Balance, December 31, 1997......................  59,000    $0.002     118
     Granted.......................................      --        --      --
     Cancelled.....................................      --        --      --
     Exercised.....................................      --        --      --
                                                     ------    ------    ----
   Balance, December 31, 1998......................  59,000    $0.002    $118
                                                     ======    ======    ====
</TABLE>

  As of December 31, 1997 and 1998, options to purchase 5,000 and 56,000 shares
of common stock were exercisable.

                                      F-33
<PAGE>

                           Netranscend Software, Inc.
                         (a development stage company)

                   Notes to Financial Statements--(Continued)


  The following table summarizes information for stock options outstanding at
December 31, 1998:

<TABLE>
<CAPTION>
                                                Options
                  Options Outstanding         Exercisable
            ---------------------------------------------
                                   Weighted
                                    Average
                                   Remaining
                                  Contractual
            Exercise    Number       Life       Number
             Price    Outstanding   (Years)   Exercisable
            --------  ----------- ----------- -----------
           <S>        <C>         <C>         <C>
            $  0.002    59,000        3.7       56,000
                        ======                  ======
</TABLE>

  The pro forma disclosures for net loss and net loss per share have not been
presented as the results would be the same as the net loss and net loss per
share as reported.

7. Subsequent Events

  On March 25, 1999, the Company was acquired by Mediaplex, Inc. ("Mediaplex")
in exchange for a note issued to the Company's sole shareholder payable in four
annual installments, and for 1,979,000 shares of Mediaplex's common stock. The
note will be paid in installments of $110,000 due on March 25, 2000, 2001 and
2003 and $100,000 on March 25, 2002. Mediaplex delivered 1,679,000 shares of
common stock immediately after the closing date and deposited the remaining
300,000 shares of common stock into an escrow fund. The escrow fund period
expires two years after the closing date, subject to fulfilling pending
unsatisfied claims, if any. At the end of the escrow period or resolution of
the unsatisfied claims, the remaining 300,000 shares of common stock will be
delivered to the sole shareholder.

  All vested and unvested options of the Company were cancelled at the closing
date of this acquisition.

                                      F-34
<PAGE>

      [INSIDE BACK COVER OF PROSPECTUS CONTAINS CLIENT'S NAMES AND LOGOS]

                            [PICTURES OF 6 PERSONS]
Caption below the pictures of people: Delivering a customized message to the
right target in real time.


Caption: Some of our Clients


[LOGOS FOR 11 CLIENTS]

Caption: Some of our Business and Marketing Alliances

[LOGOS FOR 5 ALLIANCES]

Note: The clients listed above represent those of our top 15 clients based on
gross revenues for the nine-month period ending September 30,1999 who are both
current clients and have approved the inclusion of their logos in this
prospectus. DATEK Online, ShopNow.com and Publicis & Hal Riney accounted for
approximately 17%, 11% and 10% of our revenues during the nine-month period
ending September 30, 1999.

The business and marketing alliances listed above represent all of the
companies for which we have written or oral agreements as of September 30, 1999
to work together to provide services to our clients, and from which we have
obtained permission to use their logos.
<PAGE>

                                6,000,000 Shares


                              [LOGO OF MEDIAPLEX]


                                  Common Stock


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

                                   PROSPECTUS
                                       , 1999

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


                                Lehman Brothers

                                    SG Cowen

                           U.S. Bancorp Piper Jaffray

                            Fidelity Capital Markets

             a division of National Financial Services Corporation
<PAGE>

                                    PART II

                     INFORMATION NOT REQUIRED IN PROSPECTUS

Item 13. Other Expenses of Issuance and Distribution

  The following table sets forth the costs and expenses, other than the
underwriting discount payable by Mediaplex in connection with the sale of
common stock being registered. All amounts are estimates except the SEC
registration fee and the NASD filing fee.

<TABLE>
   <S>                                                               <C>
   SEC registration fee............................................. $   19,460
   NASD filing fee..................................................      7,500
   Nasdaq National Market listing fee...............................     95,000
   Printing and engraving costs.....................................    250,000
   Legal fees and expenses..........................................    350,000
   Accounting fees and expenses.....................................    275,000
   Blue Sky fees and expenses.......................................      5,000
   Transfer agent and registrar fees................................     10,000
   Miscellaneous expenses...........................................     38,040
                                                                     ----------
     Total.......................................................... $1,050,000
                                                                     ==========
</TABLE>

Item 14. Indemnification of Directors and Officers

  Section 145 of the Delaware General Corporation Law permits a corporation to
include in its charter documents, and in agreements between the corporation and
its directors and officers, provisions expanding the scope of indemnification
beyond that specifically provided by the current law.

  Article IX of the Registrant's Amended and Restated Certificate of
Incorporation provides for the indemnification of directors to the fullest
extent permissible under Delaware law.

  Article VI of the Registrant's Amended and Restated Bylaws provides for the
indemnification of officers, directors and third parties acting on behalf of
the Registrant if such persons act in good faith and in a manner reasonably
believed to be in and not opposed to the best interests of the Registrant, and,
with respect to any criminal action or proceeding, the indemnified party had no
reason to believe his or her conduct was unlawful.

  The Registrant has entered into indemnification agreements with its directors
and executive officers, in addition to indemnification provided for in the
Registrant's Amended and Restated Bylaws, and intends to enter into
indemnification agreements with any new directors and executive officers in the
future.

  The Underwriting Agreement (Exhibit 1.1 hereto) provides for indemnification
by the Underwriters of the Registrant and its executive officers and directors
for certain liabilities, including liabilities arising under the Securities
Act, in connection with matters specifically provided in writing by the
Underwriters for inclusion in the Registration Statement.

Item 15. Recent Sales of Unregistered Securities

  During the past three years, the Registrant has issued unregistered
securities to a limited number of entities and persons as described below:

    (a) From September 1, 1996 to September 30, 1999, the Registrant issued
  and sold common stock to various entities and persons at per share purchase
  prices, as follows:

     (1) In September and October 1996, the Registrant issued and sold to
         Michael Schwartz an aggregate of 2,460,000 shares at a purchase
         price of $0.0001 per share, in connection with the Registrant's
         founding;

                                      II-1
<PAGE>

     (2) In September 1996, the Registrant issued and sold 350,000 shares
         and 250,000 shares, to Raifman & Edwards LLP and PointBreak
         Ventures, LLC, respectively, at a purchase price of $0.0001 per
         share, in payment for past services rendered to the Registrant;

     (3) In October 1996 and January 1997, the Registrant issued and sold
         1,600,000 shares to Eugene Jarvis, at a purchase price of $0.05
         per share;

     (4) In December 1996, the Registrant issued and sold an aggregate of
         800,000 shares to Kuni Research, at a purchase price of $0.05 per
         share;

     (5) During 1997, the Registrant issued and sold 220,000 shares and
         995,338 shares to non-employee investors at a purchase price of
         $0.05 per share and $0.30 per share, respectively;

     (6) In June 1997, the Registrant issued a convertible promissory note
         to Michael Schwartz in payment for past services rendered, which
         was converted into 4,643,228 shares at a conversion rate of $0.05
         per share in June 1997. In April 1998, the Registrant repurchased
         these shares, and issued in exchange a convertible promissory note
         to Michael Schwartz. In July 1998, Michael Schwartz transferred
         these shares to Raifman & Edwards, LLP. In March 1999, Raifman &
         Edwards converted the principal and interest of this note into
         4,643,228 shares at a conversion rate of $0.05 per share;

     (7) In July 1997, the Registrant issued a convertible promissory note
         to Raifman & Edwards, LLP, in payment for past services rendered,
         which in March 1999 was converted into 947,009 shares at a
         conversion rate of $0.075 per share;

     (8) In February 1998, the Registrant issued and sold to non-employee
         investors 76,000 shares at a purchase price of $0.50 per share;

     (9) In June 1998, the Registrant issued and sold to a former employee,
         Joshua Grant, 232,290 shares at a purchase price of $0.65 per
         share;

    (10) In January and March 1999, the Registrant issued and sold to an
         employee, Jay Goodman, 13,333 shares and to a non employee, Seth
         Harmon, 10,000 shares, in payment for past services rendered at
         prices of $1.13 and $1.29 per share, respectively; and

    (11) In January 1999, the Registrant, in exchange for services
         rendered, issued and sold to Glenn Argenbright, an employee,
         200,000 shares for a purchase price of $0.62 per share under our
         1997 Stock Plan.

    (b) From October 31, 1996 to September 30, 1999, the Registrant issued to
  certain of its employees, officers, directors and consultants options to
  purchase an aggregate of 9,416,398 shares of common stock of the
  Registrant, at exercise prices ranging from $0.05 per share to $6.50 per
  share, pursuant to the Registrant's 1997 Stock Plan and 1999 Stock Plan,
  and Amended and Restated 1999 Stock Plan.

    (c) From October 31, 1996 to September 30, 1999, the Registrant issued an
  aggregate of 371,667 shares of common stock to employees, directors and
  consultants of the Registrant upon the exercise of options at exercise
  prices ranging from $0.05 to $3.25 per share.

    (d) On January 11, 1999, the Registrant issued to Timothy Favia, an
  employee, a warrant to purchase an aggregate of 500,000 shares of common
  stock at an exercise price of $0.50 per share.

    (e) On January 26, 1999, the Registrant issued and sold an aggregate of
  1,206,000 shares of Series A preferred stock to 37 investors at a purchase
  price of $1.25 per share or an aggregate purchase price of $1,507,500.

    (f) On March 25, 1999, the Registrant issued and sold an aggregate of
  1,979,000 shares of common stock valued at $1.31 per share to Ruiqing Jiang
  in connection with the Registrant's acquisition of Netranscend Software,
  Inc., of which Mr. Jiang was the sole shareholder.

                                      II-2
<PAGE>

    (g) On June 15, 1999, the Registrant issued and sold an aggregate of
  4,500,000 shares of Series B preferred stock to 36 investors at a purchase
  price of $2.00 per share, or an aggregate purchase price of $9,000,000.

    (h) On June 15, 1999, the Registrant issued to Retail Ventures
  International, Inc. and Zeron Capital, Inc. warrants to purchase 150,000
  shares and 125,000 shares of Series B preferred stock at an exercise price
  of $2.00 per share.

    (i) On June 15, 1999, the Registrant issued to Retail Ventures
  International, Inc. a warrant to purchase an aggregate of 100,000 shares of
  common stock at an exercise price of $0.50 per share.

    (j) On August 6, 1999, the Registrant issued and sold an aggregate of
  4,000,000 shares of Series C preferred stock to 14 investors at a purchase
  price of $3.59 per share, or an aggregate purchase price of $14,360,000.

  The issuances described in paragraphs (a) (1) through (10) and (d) through
(j) above were deemed to be exempt from registration under the Securities Act
in reliance on Section 4(2) of the Securities Act as transactions by an issuer
not involving a public offering. The sales of securities described in
paragraphs a(11), (b) and (c) above were deemed to be exempt from the
registration requirements of the Securities Act in reliance on Rule 701
promulgated under Section 3(b) of the Securities Act as transactions by an
issuer pursuant to compensatory benefit plans and contracts relating to
compensation as provided under such Rule 701. The recipients of securities in
each such transaction represented their intention to acquire the securities for
investment only and not with a view to or for sale in connection with any
distribution thereof and appropriate legends were affixed to the share
certificates and other instruments issued in such transactions. The issuance of
warrants to purchase stock described in paragraphs (h) and (i) above did not
require registration under the Securities Act, or an exemption therefrom,
insofar as such grants did not involve a "sale" of securities as such term is
used in Section 2(3) of the Securities Act. All recipients either received
adequate information about the Registrant or had access, through employment or
other relationships, to information about the Registrant.

Item 16. Exhibits and Financial Statement Schedules

  (a) Exhibits

<TABLE>
<CAPTION>
 Exhibit
 Number
 -------
 <C>     <S>
  1.1**  Form of Underwriting Agreement.

  2.1**  Agreement and Plan of Reorganization between Registrant, Netranscend
          Software, Inc. and Ruiqing "Barclay" Jiang, dated March 8, 1999.

  3.1**  Form of the Amended and Restated Certificate of Incorporation of the
          Registrant to be in effect after the closing of the offering made
          under this Registration Statement.

  3.2**  Form of the Amended and Restated Bylaws of the Registrant to be in
          effect after the closing of the offering made under this Registration
          Statement.

  4.1**  Warrant to purchase 500,000 shares of Common Stock of the Registrant,
          dated January 11, 1999, held by Timothy Favia.

  4.2**  Warrant to purchase 100,000 shares of Common Stock of the Registrant,
          dated June 15, 1999, held by Retail Ventures International, Inc.

  4.3**  Warrant to purchase 150,000 shares of Series B Preferred Stock of the
          Registrant, dated June 15, 1999, held by Retail Ventures
          International, Inc.

  4.4**  Warrant to purchase 125,000 shares of Series B Preferred Stock of the
          Registrant, dated June 15, 1999, held by Zeron Capital, Inc.

  4.5**  Specimen Common Stock Certificate.

  5.1    Opinion of Wilson Sonsini Goodrich & Rosati, Professional Corporation.

 10.1**  Form of Indemnification Agreement between the Registrant and each of
          its directors and officers.

 10.2**  Amended and Restated 1999 Stock Plan and form of agreements
          thereunder.

</TABLE>

                                      II-3
<PAGE>

<TABLE>
<CAPTION>
 Exhibit
  Number
 -------
 <C>      <S>
 10.3**   1999 Employee Stock Purchase Plan and form of agreements thereunder.

 10.4**   1997 Stock Plan and form of agreements thereunder.

 10.5**   Basic Lease Agreement, First Amendment and Basic Lease Information
           thereto, between R&E Holdings, LLC and Persis Corporation and
           BidCom, Inc., dated September 24, 1999, February 1, 1997 and July
           31, 1998, respectively.
 10.6**   Sublease, dated July 9, 1999, with Telocity, Inc.

 10.7**   Employment Agreement with Gregory R. Raifman, dated February 19,
           1999.

 10.8**   Employment Agreement with Jon L. Edwards, dated February 19, 1999.

 10.9**   Employment Agreement with Walter Haefeker, dated February 19, 1999.

 10.10**  Employment Agreement with Ruiqing "Barclay" Jiang, dated March 24,
           1999.

 10.11**  Employment Agreement with Sandra L. Abbott, dated August 6, 1999.

 10.12+** Technology Integration and Services Agreement between the Registrant
           and DoubleClick, Inc., dated July 22, 1999.
 10.13**  Developer Package Agreement, dated July 26, 1999, between the
           Registrant and SAP Labs, Inc.

 10.14**  Memorandum of Understanding, dated September 22, 1999, between the
           Registrant and Ariba Technologies, Inc.

 10.15**  Letter Agreement, dated September 23, 1999, between the Registrant
           and OTP Software, Inc.

 10.16**  Letter Agreement, dated May 20, 1999, between the Registrant and Icon
           Medialab Inc.

 10.17**  Letter Agreement, dated August 5, 1999, between the Registrant and
           Across Media Networks, L.L.C.

 10.18**  Shareholders' Rights Agreement, dated July 30, 1999.

 23.1     Consent of PricewaterhouseCoopers LLP, independent accountants.

 23.2     Consent of PricewaterhouseCoopers LLP, independent accountants.

 23.3     Consent of Counsel (see Exhibit 5.1).

 24.1**   Power of Attorney (see page II-5).

 27.1**   Financial Data Schedule.
</TABLE>
- --------
**Previously filed.
 +Confidential treatment requested.

Item 17. Undertakings

  The undersigned Registrant 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.

  Insofar as indemnification by the Registrant for liabilities arising under
the Securities Act may be permitted to directors, officers and controlling
persons of the Registrant pursuant to the provisions referenced in Item 14 of
this Registration Statement or otherwise, the Registrant 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 Registrant of expenses incurred or
paid by a director, officer or controlling person of the Registrant in the
successful defense of any action, suit or proceeding) is asserted by a
director, officer or controlling person in connection with the securities being
registered hereunder, the Registrant will, unless in the opinion of its counsel
the matter has been settled by controlling precedent, submit

                                      II-4
<PAGE>

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 Registrant hereby undertakes that:

    (1) For purposes of determining any liability under the Securities Act,
  the information omitted from 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 Registrant 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>

                                   SIGNATURES

  Pursuant to the requirements of the Securities Act of 1933, as amended, the
registrant has duly caused this Amendment No. 4 to Registration Statement to be
signed on its behalf by the undersigned, thereunto duly authorized, in the City
of San Francisco, State of California, on the 12th day of November, 1999.

                                          MEDIAPLEX, INC.

                                                 /s/ Gregory R. Raifman
                                          By:__________________________________
                                                     Gregory R. Raifman
                                                Chairman and Chief Executive
                                                          Officer

                               POWER OF ATTORNEY

  Pursuant to the requirements of the Securities Act of 1933, as amended, this
Amendment No. 4 to Registration Statement has been signed by the following
persons in the capacities and on the dates indicated below.

<TABLE>
<CAPTION>
              Signature                         Title                  Date
              ---------                         -----                  ----

 <C>                                  <S>                        <C>
        /s/ Gregory R. Raifman        Chairman and Chief           November 12,
 ____________________________________  Executive Officer               1999
          Gregory R. Raifman           (Principal Executive
                                       Officer)

                  *                   Senior Vice President,       November 12,
 ____________________________________  Chief Financial Officer         1999
           Sandra L. Abbott            and Secretary
                                       (Principal Accounting
                                       Officer)

                  *                   President and Director       November 12,
 ____________________________________                                  1999
            Jon L. Edwards

                  *                   Director                     November 12,
 ____________________________________                                  1999
       Lawrence D. Lenihan, Jr.

                  *                   Director                     November 12,
 ____________________________________                                  1999
           Peter S. Sealey
                  *                   Director                     November 12,
 ____________________________________                                  1999
           James DeSorrento

                  *                   Director                     November 12,
 ____________________________________                                  1999
          A. Brooke Seawell

      /s/ Gregory R. Raifman
 *By: _______________________________
          Gregory R. Raifman
           Attorney-in-Fact

</TABLE>

                                      II-6
<PAGE>

                                 EXHIBIT INDEX

<TABLE>
<CAPTION>
 Exhibit
  Number
 -------
 <C>      <S>
  1.1**   Form of Underwriting Agreement.

  2.1**   Agreement and Plan of Reorganization between Registrant, Netranscend
           Software, Inc. and Ruiqing "Barclay" Jiang, dated March 8, 1999.

  3.1**   Form of the Amended and Restated Certificate of Incorporation of the
           Registrant to be in effect after the closing of the offering made
           under this Registration Statement.

  3.2**   Form of the Amended and Restated Bylaws of the Registrant to be in
           effect after the closing of the offering made under this
           Registration Statement.

  4.1**   Warrant to purchase 500,000 shares of Common Stock of the Registrant,
           dated January 11, 1999, held by Timothy Favia.

  4.2**   Warrant to purchase 100,000 shares of Common Stock of the Registrant,
           dated June 15, 1999, held by Retail Ventures International, Inc.

  4.3**   Warrant to purchase 150,000 shares of Series B Preferred Stock of the
           Registrant, dated June 15, 1999, held by Retail Ventures
           International, Inc.

  4.4**   Warrant to purchase 125,000 shares of Series B Preferred Stock of the
           Registrant, dated June 15, 1999, held by Zeron Capital, Inc.

  4.5**   Specimen Common Stock Certificate.

  5.1     Opinion of Wilson Sonsini Goodrich & Rosati, Professional
           Corporation.

 10.1**   Form of Indemnification Agreement between the Registrant and each of
           its directors and officers.

 10.2**   Amended and Restated 1999 Stock Plan and form of agreements
           thereunder.

 10.3**   1999 Employee Stock Purchase Plan and form of agreements thereunder.

 10.4**   1997 Stock Plan and form of agreements thereunder.

 10.5**   Basic Lease Agreement, First Amendment and Basic Lease Information
           thereto, between R&E Holdings, LLC and Persis Corporation and
           BidCom, Inc., dated September 24, 1999, February 1, 1997 and July
           31, 1998, respectively.

 10.6**   Sublease, dated July 9, 1999, with Telocity, Inc.

 10.7**   Employment Agreement with Gregory R. Raifman, dated February 19,
           1999.

 10.8**   Employment Agreement with Jon L. Edwards, dated February 19, 1999.

 10.9**   Employment Agreement with Walter Haefeker, dated February 19, 1999.

 10.10**  Employment Agreement with Ruiqing "Barclay" Jiang, dated March 24,
           1999.

 10.11**  Employment Agreement with Sandra L. Abbott, dated August 6, 1999.

 10.12+** Technology Integration and Services Agreement between the Registrant
           and DoubleClick, Inc., dated July 22, 1999.

 10.13**  Developer Package Agreement, dated July 26, 1999, between the
           Registrant and SAP Labs, Inc.

 10.14**  Memorandum of Understanding, dated September 22, 1999, between the
           Registrant and Ariba Technologies, Inc.

 10.15**  Letter Agreement, dated September 23, 1999, between the Registrant
           and OTP Software, Inc.

 10.16**  Letter Agreement, dated May 20, 1999, between the Registrant and Icon
           Medialab Inc.

 10.17**  Letter Agreement, dated August 5, 1999, between the Registrant and
           Across Media Networks, L.L.C.

 10.18**  Shareholders' Rights Agreement, dated July 30, 1999.

 23.1     Consent of PricewaterhouseCoopers LLP, independent accountants.

 23.2     Consent of PricewaterhouseCoopers LLP, independent accountants.

 23.3     Consent of Counsel (see Exhibit 5.1).

 24.1**   Power of Attorney (see page II-5).

 27.1**   Financial Data Schedule.
</TABLE>
- --------
** Previously filed.
 + Confidential treatment requested.

<PAGE>


                                                                Exhibit 5.1

                             November 12, 1999

Mediaplex, Inc.
131 Steuart Street, Fourth Floor
San Francisco, California 94105-1230

  Re: Registration Statement on Form S-1

Ladies and Gentlemen:

  We have examined the Registration Statement on Form S-1 filed by you with the
Securities and Exchange Commission ("SEC") on September 2, 1999 (Registration
No. 333-86459), as amended by Amendment Nos. 1, 2, 3 and 4 thereto filed with
the SEC on September 16, 1999, October 8, 1999, October 29, 1999 and November
12, 1999, respectively (the "Registration Statement"), in connection with the
Securities Act of 1933, as amended, of up to 6,000,000 shares of your Common
Stock, par value $0.0001 and an over-allotment option granted to the
underwriters of the offering to purchase up to 900,000 shares from you
(collectively, the "Shares"). We understand that the Shares are to be sold to
the underwriters of the offering for resale to the public as described in the
Registration Statement. As your legal counsel, we have examined the proceedings
taken, and are familiar with the proceedings proposed to be taken, by you in
connection with the sale and issuance of the Shares.

  It is our opinion that, upon completion of the proceedings being taken or
contemplated by us as your counsel, to be taken prior to the issuance of the
Shares, including the proceeding being taken in order to permit such
transaction to be carried out in accordance with applicable state securities
laws, the Shares, when issued and sold in the manner described in the
Registration Statement and in accordance with the resolutions adopted by the
Board of Directors of the Company, will be duly authorized, legally and validly
issued, fully paid and nonassessable.

  We consent to the use of this opinion as an exhibit to the Registration
Statement and further consent to the use of our name wherever appearing in the
Registration Statement, including the Prospectus constituting a part thereof
and any amendments thereto.

                                          Very truly yours,

                                          Wilson Sonsini Goodrich & Rosati
                                          Professional Corporation

                                          /s/ Wilson Sonsini Goodrich & Rosati

<PAGE>

                                                                    Exhibit 23.1

                       CONSENT OF INDEPENDENT ACCOUNTANTS

We hereby consent to the use in this Registration Statement on Form S-1 of our
report dated July 30, 1999, except for Note 10, which is as of September 1,
1999, relating to the financial statements of Mediaplex, Inc., which appear in
such Registration Statement. We also consent to the references to us under the
headings "Experts" in such Registration Statement.

/s/ PricewaterhouseCoopers LLP

San Francisco, California

November 11, 1999

<PAGE>

                                                                    Exhibit 23.2

                       CONSENT OF INDEPENDENT ACCOUNTANTS

We hereby consent to the use in this Registration Statement on Form S-1 of our
report dated July 23, 1999, relating to the financial statements of Netranscend
Software, Inc., which appear in such Registration Statement. We also consent to
the reference to us under the headings "Experts" in such Registration
Statement.

/s/ PricewaterhouseCoopers LLP

San Francisco, California

November 11, 1999


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