ONCOR INC, S-3/A, 1997-02-28

ONCOR INC
S-3/A, 1997-02-28
IN VITRO & IN VIVO DIAGNOSTIC SUBSTANCES

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<PAGE> 1

AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON FEBRUARY 28, 1997
REGISTRATION NO. 333-20425

================================================================================
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
-------------------

AMENDMENT NO. 1
TO

FORM S-3
REGISTRATION STATEMENT
UNDER THE SECURITIES ACT OF 1933
-------------------
ONCOR, INC.
(Exact name of Registrant as specified in its charter)
-------------------

MARYLAND 52-1310084
(State or other jurisdiction of (I.R.S. Employer
incorporation or organization) Identification Number)

209 PERRY PARKWAY, GAITHERSBURG, MARYLAND 20877
(301) 963-3500
(Address, including zip code, and telephone number,
including area code, of Registrant's principal executive offices)
-------------------
RICHARD R. PLUMRIDGE, ESQ.
ALEXANDER D. LYNCH, ESQ.
BROBECK, PHLEGER & HARRISON LLP
1633 Broadway, 47th Floor
New York, New York 10019
(212) 581-1600
(Name, address, including zip code, and telephone number,
including area code, of agent for service of process)

APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC: As
soon as practicable on or after this Registration Statement is declared
effective.

If the only securities being registered on this Form are being offered
pursuant to dividend or interest reinvestment plans, please check the following
box. [ ]

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, other than securities offered only in connection with
dividend or interest reinvestment plans, check the following box. [X]

If this Form is filed to register additional securities for an
offering pursuant to Rule 462(b) under the Securities Act, please 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 delivery of the prospectus is expected to be made pursuant to Rule
434, please check the following box. [ ]

CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
================================================================================================================================
Proposed maximum Proposed maximum
Title of shares to be Amount to be aggregate price per aggregate offering Amount of registration
registered registered unit(1) price(1) fee(3)
- --------------------------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C> <C> <C>
Common Stock, $.01 par
value(2) 4,907,645 Shares $4.43 $20,092,175 $6.00
================================================================================================================================
</TABLE>

(1) Estimated pursuant to Rule 457(c) solely for the purpose of computing
the registration fee based upon the average of the high and low prices
of the Common Stock, as reported on the American Stock Exchange as of
a date which is within five business days of the date of this
Registration Statement.
(2) Pursuant to Rule 416, there are also being registered such
indeterminable additional securities as may be issued to prevent
dilution resulting from stock dilution, stock splits, stock dividends
or similar transactions or by reason of changes in the conversion
price of certain securities in accordance with the terms thereof.

(3) A registration fee of $6,082.53 has previously been paid in connection
with Registration Statement No. 333-20425, filed on January 24, 1996
(to which this filing constitutes Pre-Effective Amendment No. 1)
relating to 4,903,170 of the shares to be registered hereby.

THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR DATES
AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL FILE
A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION STATEMENT
SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(a) OF THE
SECURITIES ACT OF 1933 OR UNTIL THE REGISTRATION STATEMENT SHALL BECOME
EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(a),
MAY DETERMINE.
================================================================================
<PAGE> 2
PROSPECTUS

4,907,645 SHARES

ONCOR, INC.
COMMON STOCK
---------------------------

This Prospectus relates to the public offering, which is not being
underwritten, of up to 4,907,645 shares (the "Shares") of Common Stock, par
value $.01 per share, of Oncor, Inc. ("Oncor" or the "Company"). 4,903,170 of
these shares are issuable by the Company (i) upon the conversion of 6%
Convertible Debentures due December 30, 2001 (the "Debentures") and (ii) upon
exercise of certain warrants (the "Warrants") to purchase shares of Common
Stock and (iii) upon the exercise of certain options to purchase additional
shares of Common Stock (the "Options"). The remaining 4,475 shares were issued
to a stockholder in an unrelated transaction. The Shares may be offered by
holders of the Debentures who subsequently convert their Debentures, the
holders of the Warrants who subsequently exercise their Warrants, the holders
of the Options who exercise their Options and the unrelated stockholder (the
"Selling Stockholders").

The Shares may be offered by the Selling Stockholders from time to
time in transactions on the American Stock Exchange, in negotiated
transactions, or a combination of such methods of sale, at fixed prices which
may be changed, at market prices prevailing at the time of sale, at prices
related to prevailing market prices or at negotiated prices. The Selling
Stockholders may effect such transactions by selling the Shares to or through
broker-dealers, and such broker-dealers may receive compensation in the form of
discounts, concessions or commissions from the Selling Stockholders and/or the
purchasers of the Shares for whom such broker-dealers may act as agents or to
whom they sell as principals, or both (which compensation as to a particular
broker-dealer might be in excess of customary commissions). In order to comply
with the securities laws of certain states, if applicable, the Shares will be
sold in such jurisdictions only through registered or licensed brokers or
dealers. The Selling Stockholders may transfer their Debentures or Warrants
under certain circumstances to other persons who may, in turn, resell Shares in
the manner described above. In addition, the Selling Stockholders may pledge
or make gifts of their Shares and such Shares may also be sold by the pledgees
or transferees. To the extent required, the specific Shares to be sold, the
names of the Selling Stockholders, the public offering price, the names of any
such agent, dealer or underwriter, and any applicable commission or discount
with respect to any particular offer will be set forth in an accompanying
Prospectus Supplement. See "Selling Stockholders" and "Plan of Distribution."

None of the proceeds from the sale of the shares issued upon
conversion of the Debentures (the "Debenture Shares") by the Selling
Stockholders will be received by the Company. The Company will receive
aggregate proceeds of up to $11,250,000 upon the exercise of the Warrants and
the Options. See "Issuance of Shares and Use of Proceeds." The Company has
agreed to bear certain expenses (other than underwriting discounts and selling
commissions and fees and disbursements of counsel and other advisors to the
Selling Stockholders) in connection with the registration of the Shares. The
Company has agreed to indemnify the Selling Stockholders and their affiliates
against certain liabilities, including liabilities under the Securities Act of
1933, as amended (the "Securities Act"). The Selling Stockholders have agreed
to indemnify the Company and its affiliates against certain liabilities,
including liabilities under the Securities Act under certain circumstances.

AN INVESTMENT IN THE SHARES OFFERED HEREBY INVOLVES A HIGH DEGREE OF RISK.
SEE "RISK FACTORS" BEGINNING ON PAGE 3.

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

The Common Stock of the Company is traded on the American Stock
Exchange under the symbol "ONC." The last reported sales price of the Company's
Common Stock on the American Stock Exchange on February 25, 1997 was $4.50 per
share.

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

THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE
SECURITIES AND EXCHANGE COMMISSION OR ANY STATE SECURITIES
COMMISSION PASSED UPON THE ACCURACY OR ADEQUACY OF THIS
PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS
A CRIMINAL OFFENSE.

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

THE DATE OF THIS PROSPECTUS IS FEBRUARY 28, 1997

<PAGE> 3
No person has been authorized to give any information or to make any
representations other than those contained in this Prospectus in connection
with the offering made hereby, and if given or made, such information or
representations must not be relied upon as having been authorized by the
Company, any Selling Stockholder or by any other person. Neither the delivery
of this Prospectus nor any sale made hereunder shall, under any circumstances,
create any implication that the information herein is correct as of any time
subsequent to the date hereof. This Prospectus does not constitute an offer to
sell or a solicitation of an offer to buy the Shares to any person or by anyone
in any jurisdiction in which such offer or solicitation may not lawfully be
made.

AVAILABLE INFORMATION

The Company has filed with the Securities and Exchange Commission (the
"Commission") a Registration Statement on Form S-3 under the Securities Act
with respect to the Common Stock offered hereby. This Prospectus does not
contain all of the information set forth in the Registration Statement and the
exhibits and the schedules thereto. For further information with respect to
the Company and such Common Stock, reference is made to the Registration
Statement and exhibits and schedules thereto. Statements contained in this
Prospectus as to the contents of any contract or other document referred to are
not necessarily complete, and, with respect to any contract or other document
filed as an exhibit to the Registration Statement, each such statement is
qualified in all respects by reference to such exhibit. Copies of the
Registration Statement and the exhibits thereto are on file at the offices of
the Commission and may be obtained upon payment of the prescribed fee or may be
examined without charge at the public reference facilities of the Commission
described below.

The Company is subject to the reporting requirements of the Securities
Exchange Act of 1934, as amended (the "Exchange Act"), and in accordance
therewith files annual and quarterly reports, proxy statements and other
information with the Commission. Such reports, proxy statements and other
information may be inspected, and copies of such material may be obtained upon
payment of the prescribed fees, at the Commission's Public Reference Section,
Room 1024, 450 Fifth Street, N.W., Washington D.C. 20549, as well as at the
Commission's Regional Offices at Seven World Trade Center, New York, New York
10048, and Citicorp Center, 500 West Madison Street, Suite 1400, Chicago,
Illinois 60661-2511, or may be obtained from the Commission's Internet site on
the world wide web at http://www.sec.gov. Copies of such material can be
obtained in person from the Public Reference Section of the Commission at its
principal office located at 450 Fifth Street, N.W., Washington, D.C. 20549,
upon payment of the prescribed fees.

The Common Stock of the Company is traded on the American Stock
Exchange, and in accordance therewith, annual and quarterly reports, proxy
statements and other information concerning the Company may be inspected at the
American Stock Exchange's offices located in New York.

INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

The following documents filed with the Commission are hereby
incorporated by reference in this Prospectus: (1) the Annual Report of the
Company on Form 10-K for the fiscal year ended December 31, 1995 (the "1995
Form 10-K"); (2) the Quarterly Reports of the Company on Form 10-Q for the
quarters ended March 31, 1996, June 30, 1996 and September 30, 1996; (3) the
Proxy Statement of the Company in connection with the Annual Meeting of the
Stockholders held on July 9, 1996; and (4) the Current Report of the Company on
Form 8-K, dated January 4, 1996.

All reports and other documents subsequently filed by the Company
pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act after the
date of this Prospectus and prior to the termination of this Offering shall be
deemed to be incorporated by reference herein and to be a part hereof from the
date of filing of such reports and documents. Any statement incorporated
herein shall be deemed to be modified or superseded for purposes of this
Prospectus to the extent that a statement contained herein or in any other
subsequently filed document which also is or is deemed to be incorporated by
reference herein modifies or supersedes such statement. Any statement so
modified or superseded shall not be deemed, except as so modified or
superseded, to constitute a part of this Prospectus.

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<PAGE> 4
The Company will provide without charge to each person to whom this
Prospectus is delivered, upon written or oral request of such person, a copy of
any or all of the foregoing documents incorporated herein by reference (other
than exhibits to such documents, unless such exhibits are specifically
incorporated by reference into such document). Requests for such documents
should be submitted in writing to Mr. John L. Coker, Vice President, Oncor,
Inc., 209 Perry Parkway, Gaithersburg, Maryland 20877.

THE COMPANY

The Company was incorporated in Maryland in July 1983. The Company's
principal offices are located at 209 Perry Parkway, Gaithersburg, Maryland
20877, and its telephone number is (301) 963-3500.

RISK FACTORS

An investment in the shares of Common Stock offered hereby involves a
high degree of risk and should not be made by any investor who cannot afford
the loss of his entire investment. Accordingly, prospective investors should
carefully consider the following factors, in addition to all of the other
information presented in this Prospectus, before purchasing any of the shares
of Common Stock offered hereby.

RISK ASSOCIATED WITH THE Her-2/neu GENE-BASED TEST SYSTEM

In November 1995, a U.S. Food and Drug Administration ("FDA") advisory
panel (the "Panel") made a recommendation against final approval of the
Company's Pre-Market Approval ("PMA") application for the use of its Her-2/neu
gene-based test system for diagnostic purposes. In October of 1996, the
Company received confirmation that the FDA had accepted the clinical utility
and the statistical model for determining the predictive value of its Her-2/neu
gene-based test system for diagnostic purposes. However, no assurance can be
given that the Company will obtain FDA approval for its Her-2/neu gene-based
test system. The failure to obtain FDA approval for its Her-2/neu gene-based
test system on a timely basis, or at all, would have a material and adverse
effect on the Company's business, financial condition and results of
operations. In the event that the Company receives FDA approval for its
Her-2/neu gene-based test system, there can be no assurance that the Company
will be capable of manufacturing the test system in commercial quantities at
reasonable costs or marketing the product successfully, that the test system
will be accepted by the medical diagnostic community, or that the market demand
for the test system will be sufficient to allow profitable sales.

HISTORY OF OPERATING LOSSES

Oncor has not been profitable since its inception in July 1983. For
the year ended December 31, 1995 and the nine months ended September 30, 1996,
the Company incurred net losses of $18.2 million and $19.2 million,
respectively. As of September 30, 1996, the accumulated deficit of the Company
was $91.9 million. The Company expects to incur additional substantial losses
in the last three months of 1996 and expects to incur additional substantial
losses in future periods. The Company is unable to predict when, or if, it
will become profitable.

NO ASSURANCE OF REGULATORY APPROVALS; GOVERNMENT REGULATION

The Company's products are subject to extensive regulation by
governmental authorities in the United States and other countries. The FDA and
comparable agencies in other countries impose substantial requirements that
must be satisfied before newly developed products may be sold for diagnostic
use. Although the Company may sell its products in the United States for
research purposes only, it may not sell such products in the United States for
diagnostic purposes until it receives approval from the FDA. The Company is
currently pursuing FDA approval of certain existing products and expects to
pursue FDA approval of certain additional products under development. There
can be no assurance that the Company will receive regulatory approval for any
of its products or, even if it does receive regulatory approval for a
particular product, that the Company will ever recover its costs in connection
with obtaining such approval. The timing of regulatory approvals is not within
the control of the Company. The

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<PAGE> 5
failure of the Company to receive requisite approval, or significant delays in
obtaining such approval, could have a material and adverse effect on the
business, financial condition and results of operations of the Company.

Approval by the FDA requires lengthy, detailed and costly laboratory
and clinical testing procedures and application preparation and defense efforts
to demonstrate a product's efficacy and safety before a product can be sold for
diagnostic use. Even if such regulatory approval is obtained for a product,
its manufacturer and its manufacturing facilities are subject to continual
review and periodic inspections by the FDA and other regulatory agencies. The
regulatory standards for manufacturing are applied stringently by the FDA.
Discovery of previously unknown problems with a product, manufacturer or
facility may result in restrictions on such product or manufacturer, including
costly recalls or even withdrawal of the product from the market. Furthermore,
approval may entail ongoing requirements for postmarketing studies. Failure to
maintain requisite manufacturing standards or discovery of previously unknown
problems could have a material and adverse effect on the Company's business,
financial condition or results of operations.

Sales of the Company's products outside the United States are also
subject to extensive regulatory requirements, which vary widely from country to
country. Diagnostic products that have not been approved by the FDA may be
exported for sale for diagnostic use outside the United States only after
receiving approval for export by the FDA. Furthermore, such products may be
exported for diagnostic use only in certain countries, generally countries
within Europe, Canada, Australia and Japan, and, then, only if the appropriate
regulatory authorities in such countries have approved such products for
diagnostic use in their respective countries. The time required to obtain such
approvals may be longer or shorter than that required for FDA approval. The
Company has received approval to market its Her-2/neu and CML gene-based test
systems for diagnostic use in Australia, Austria, Canada, Denmark, Germany,
Ireland, the Netherlands, Switzerland and the United Kingdom. This foreign
regulatory approval process includes all of the risks associated with FDA
approval set forth above.

Additionally, the Company is or may become subject to various federal,
state and local laws, regulations and recommendations relating to safe working
conditions, laboratory and manufacturing practices, the experimental use of
animals and the use and disposal of hazardous or potentially hazardous
substances, including radioactive compounds and infectious disease agents, used
in connection with the Company's research and development work. The Company is
unable to predict the extent of future government regulation.

PATENTS AND PROPRIETARY RIGHTS

The Company's success will depend in large part on its, or its
licensors, ability to obtain patents, defend its patents, maintain trade
secrets and operate without infringing upon the proprietary rights of others,
both in the United States and in foreign countries. The patent position of
firms relying upon biotechnology is highly uncertain in general and involves
complex legal and factual questions. To date there has emerged no consistent
policy regarding the breadth of claims allowed in biotechnology patents or the
degree of protection afforded under such patents. The Company relies on
certain patents and pending United States and foreign patent applications
relating to various aspects of its products. These patents and patent
applications are either owned by the Company or rights under them are licensed
to the Company. There can be no assurance that patents will issue as a result
of any such pending applications or that, if issued, such patents will be
sufficiently broad to afford protection against competitors with similar
technology. In addition, there can be no assurance that any patents issued to
the Company, or for which the Company has license rights, will not be
challenged, invalidated or circumvented, or that the rights granted thereunder
will provide competitive advantages to the Company. The commercial success of
the Company will also depend upon avoiding the infringement of patents issued
to competitors and upon maintaining the technology licenses upon which certain
of the Company's current products are, or any future products under development
might be, based. Litigation, which could result in substantial cost to the
Company, may be necessary to enforce the Company's patent and license rights or
to determine the scope and validity of others' proprietary rights. If
competitors of the Company prepare and file patent applications in the United
States that claim technology also claimed by the Company, the Company may have
to participate in interference proceedings declared by the United States Patent
and Trademark Office ("PTO") to determine the priority of invention, which
could result in substantial cost to the Company, even if the outcome is
favorable to the Company. An adverse outcome could subject the Company to
significant liabilities to third parties and require the Company to license
disputed rights from third

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<PAGE> 6
parties or cease using the technology. A United States patent application is
maintained under conditions of confidentiality while the application is pending
in the PTO, so that the Company cannot determine the inventions being claimed
in pending patent applications filed by its competitors in the PTO. Further,
United States patents do not provide any remedies for infringement that
occurred before the patent is granted.

The University of California and its licensee, Vysis, Inc. ("Vysis"),
filed suit against Oncor on September 5, 1995 for infringement of U.S. Patent
No. 5,447,841 entitled Methods and Compositions for Chromosome Specific
Staining which issued on that same date. The patent relates to a method of
performing in situ hybridization using a blocking nucleic acid that is
complementary to repetitive sequences. The Company has moved for a summary
judgment that the patent in suit is invalid, unenforceable and not infringed.
Vysis has moved for a summary judgment that the patent in suit is not invalid,
not unenforceable and infringed by the sale of Company's products. A hearing on
those and other motions was held on January 10, 1997, and no judicial rulings
on any of the motions have been made as of the date of this Registration
Statement. A failure to successfully defend against or settle this suit may
result in damages being assessed against the Company and an injunction against
the sale of some of the Company's products. The Company has attempted to
resolve the lawsuit through a negotiated settlement, but such negotiations were
unsuccessful. In connection with the suit, there can be no assurance that the
Company would be able to license the technologies underlying the patent in
question or, if available, that such license would be on terms acceptable to
the Company or that the Company would be successful in any attempt to redesign
its products or processes to avoid infringement. An unfavorable decision in
the suit, or the Company's failure to obtain a license or redesign its products
or processes, could have a material adverse effect on the Company.

The Company has licensed rights to inventions disclosed in United
States and foreign patent applications relating to methods and probes for
detecting the presence of the Fragile X syndrome. The Company believes that
its licensors are original inventors and are entitled to patent protection in
the United States, but the Company is aware that certain third parties also
have filed patent applications in the United States and abroad and claim to be
entitled to patents related to this technology. The Company has initiated an
interference proceeding with these third parties in the PTO to resolve which
party is entitled to a United States patent, if any. The application licensed
by the Company is senior in the interference. An unfavorable decision in such
a proceeding could have an adverse effect on the Company.

The Company currently has certain licenses from third parties and in
the future may require additional licenses from other parties to develop,
manufacture and market commercially viable products effectively. There can be
no assurance that such licenses will be obtainable on commercially reasonable
terms, if at all, that the patents underlying such licenses will be valid and
enforceable or that the proprietary nature of the patented technology
underlying such licenses will remain proprietary.

The Company relies substantially on certain technologies that are not
patentable or proprietary and are therefore available to the Company's
competitors. The Company also relies on certain proprietary trade secrets and
know-how that are not patentable. Although the Company has taken steps to
protect its unpatented trade secrets and know-how, in part through the use of
confidentiality agreements with its employees, consultants and certain of its
contractors, there can be no assurance that these agreements will not be
breached, that the Company would have adequate remedies for any breach, or that
the Company's trade secrets will not otherwise become known or be independently
developed or discovered by competitors.

UNCERTAINTIES RELATING TO PRODUCT DEVELOPMENT

Most of the Company's products have not been approved by the FDA and
may be sold only for research purposes. The Company has undertaken to seek FDA
approval for certain of these products, and may in the future undertake to seek
such approval for other products, and substantial additional investment,
laboratory development, clinical testing and FDA approval will be required
prior to the commercialization of such products for diagnostic purposes. There
can be no assurance that the Company will be successful in developing such
existing or future products, that such products will prove to be efficacious in
clinical trials, that required regulatory approvals can be obtained for such
products, that such products, if developed and approved, will be capable of
being manufactured

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<PAGE> 7
in commercial quantities at reasonable costs, will be marketed successfully or
will be accepted by the medical diagnostic community, or that market demand for
such products will be sufficient to allow profitable operations.

INTERNATIONAL SALES AND FOREIGN EXCHANGE RISK

The Company derived approximately $9.0 million and $6.4 million, or
56% and 51.4% of its total product revenues, from customers outside of the
United States for the year ended December 31, 1995 and the nine months ended
September 30, 1996, respectively. The Company anticipates that a significant
amount of its sales will continue outside of the United States in the
foreseeable future and that a significant amount of its sales will take place
in European countries and likely will be denominated in currencies other than
the U.S. dollar. These sales may be adversely affected by changing economic
conditions in foreign countries and by fluctuations in currency exchange rates.
Any significant decline in the applicable rates of exchange could have a
material adverse effect on the Company's business, financial condition and
results of operations. Additional risks inherent in the Company's
international business activities generally include unexpected changes in
regulatory requirements, tariffs and other trade barriers, lack of acceptance
of products in foreign markets, longer accounts receivable payment cycles,
difficulties in managing international operations, potentially adverse tax
consequences, restrictions on repatriation of earnings and the burdens of
complying with a wide variety of foreign laws. There can be no assurance that
such factors will not have a material adverse effect on the Company's future
international revenues and, consequently, on the Company's business, financial
condition and results of operations.

LIMITED MANUFACTURING EXPERIENCE

The Company's ability to conduct clinical trials on a timely basis, to
obtain regulatory approvals and to commercialize its products will depend in
part upon its ability to develop and maintain facilities to manufacture its
products, either directly or through third parties, at a competitive cost in
accordance with the FDA's prescribed current Good Manufacturing Practices
("GMP") and other regulatory requirements. Any failure to maintain
manufacturing facilities in accordance with the FDA's GMP requirements could
result in the inability of the Company to manufacture its products and may
limit the Company's ability to deliver its products to its customers, which
would have a material and adverse effect on the Company's business, financial
condition and results of operations. No assurance can be given that the
Company will be able to develop and maintain GMP facilities or engage third
parties to do so at a cost acceptable to the Company.

The Company has only limited experience in manufacturing products on a
commercial basis. The Company believes that its existing manufacturing
facilities will enable it to produce commercial quantities of its products
through 1997. No assurance can be given, however, that manufacturing or
quality control problems will not arise if the Company increases production of
its products, or if additional facilities are required in the future.

LIMITED MARKETING AND DISTRIBUTION EXPERIENCE

The Company markets and sells its products for research purposes and,
once approved by the appropriate regulatory authority, for diagnostic use,
through its direct sales forces in both Europe and the United States and
indirectly through third parties in the Pacific Rim. The Company only has
limited experience in sales, marketing and distribution. In order to market
its products directly, the Company must maintain a sales force with technical
expertise and an understanding of the Company's products. There can be no
assurance that the Company will be able to maintain such a sales force or that
the Company's direct sales and marketing efforts will be successful. In
addition, the Company's products compete with the products of many other
companies that currently have extensive and well-funded marketing and sales
operations. There can be no assurance that the Company's marketing and sales
efforts will compete successfully against such other companies. To the extent
the Company enters arrangements with third parties, any revenues received by
the Company will be dependent on the efforts of such third parties, and there
can be no assurance that such efforts will be successful.

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COMPETITION AND TECHNOLOGICAL CHANGE

The diagnostic and biotechnology industries are subject to intense
competition and rapid and significant technological change. Competitors of the
Company in the United States and in foreign countries are numerous and include,
among others, diagnostic, health care, pharmaceutical, biotechnology and
chemical companies, academic institutions, government agencies and other public
and private research organizations. Many of these competitors have
substantially greater financial and technical resources and production and
marketing capabilities than the Company. There can be no assurance that these
competitors will not succeed in developing technologies and products that are
more effective, easier to use or less expensive than those that have been or
are being developed by the Company or that would render the Company's
technology and products obsolete and noncompetitive. The Company also competes
with various companies in acquiring technology from academic institutions,
government agencies and research organizations. In addition, many of the
Company's competitors have significantly greater experience than the Company in
conducting clinical trials of new diagnostic products and in obtaining FDA and
other regulatory approvals of products for use in health care. Accordingly,
the Company's competitors may succeed in obtaining regulatory approval for
products more rapidly than the Company.

RESTRICTED USE OF THE COMPANY'S PRODUCT

The Company's current products, to the extent sold in the United
States, must be sold for research purposes only and must be labeled
accordingly. The FDA imposes distribution requirements and procedures on
companies selling products for research purposes only, including the
requirement that the seller receive specified certifications from its customer
as to the customer's intended use of the product. As a result of these
requirements, most of the Company's products, to the extent sold in the United
States, can only be sold to a limited number of customers for limited use and
can not be sold for broader commercial use without FDA approval. No assurance
can be given that the Company will receive FDA approval for its products.

GOVERNMENT FUNDING

The Company's products being sold for research purposes only are in
large part purchased by cancer researchers operating under programs funded by
the United States and French national governments. These products are also
purchased by researchers involved in the human genome project, which is
likewise principally funded by the governments. There can be no assurance that
such government funding will continue at its current level. The Company would
be adversely affected by decreases in or changes in the kinds of government
funding for cancer research or human genome research.

ATTRACTION AND RETENTION OF KEY PERSONNEL

The Company's ability to successfully develop marketable products and
to maintain a competitive position will depend in large part on its ability to
attract and retain highly qualified scientific and management personnel. The
Company is highly dependent upon the principal members of its management,
scientific staff and science advisory board. Competition for such personnel
and advisors is intense, and there can be no assurance that the Company will be
able to continue to attract and retain such personnel.

UNCERTAINTY RELATED TO HEALTH CARE REFORM MEASURES AND THIRD-PARTY
REIMBURSEMENT

Political, economic and regulatory influences are likely to lead to
fundamental change in the health care industry in the United States. Numerous
proposals for comprehensive reform of the nation's health care system have been
introduced in Congress over the past two years. In addition, certain states
are considering various health care reform proposals. The Company anticipates
that Congress and state legislatures will continue to review and assess
alternative health care delivery systems and payment methodologies, and that
public debate of these issues will likely continue in the future. Due to
uncertainties regarding the ultimate features of reform initiatives and their
enactment and implementation, the Company cannot predict which, if any, reforms
will be adopted, when they may be adopted, or what impact they may have on the
Company. The Company's ability to earn sufficient returns on its products may
also depend in part on the extent to which reimbursement for the costs of such
products will be

-7-
<PAGE> 9
available from government health administration authorities, private health
insurers and other organizations. Third-party payors are increasingly
challenging the price and cost effectiveness of medical products and services.
Significant uncertainty exists as to the reimbursement status of newly approved
health care products, and there can be no assurance that adequate reimbursement
will be available or sufficient to allow the Company to sell its products on a
competitive basis.

ADDITIONAL FINANCING REQUIREMENTS AND ACCESS TO CAPITAL FUNDING

The Company has expended and will continue to expend in the future
substantial funds to continue the research and development of its products,
conduct clinical trials, make capital expenditures, establish additional
manufacturing capability, and market its products. The Company believes that
its existing funds will be adequate to finance its operations through 1997.
This belief is based on the Company's current research and development plans,
the current regulatory environment, historical industry experience in the
development of biotechnology products and general economic conditions. However,
the Company's cash requirements may vary materially from those now planned as a
result of unforeseen changes that could consume a significant portion of the
available resources before such time. To the extent that funds expected to be
generated from the Company's operations are insufficient to meet current or
planned operating requirements, the Company will seek to obtain additional
funds through equity or debt financing, collaborative or other arrangements
with corporate partners and others, and from other sources. No assurance can
be given that additional financing will be available when needed or on terms
acceptable to the Company. If adequate funds are not available, the Company
may be required to delay or to eliminate expenditures for certain of its
products or to license to third parties the rights to commercialize products or
technologies that the Company would otherwise seek to develop itself.

PRODUCT LIABILITY

The testing, marketing and sale of health care products could expose
the Company to the risk of product liability claims. A product liability claim
could have a material and adverse effect on the business, results of operations
or financial condition of the Company. The Company currently maintains product
liability insurance coverage of $5.0 million per occurrence. There can be no
assurance, however, that this coverage will be adequate to protect the Company
against future product liability claims or that product liability insurance
will be available to the Company in the future on acceptable terms, if at all.

ENVIRONMENTAL RISKS

The manufacturing and research and development processes of the
Company involve the controlled use of hazardous materials. The Company is
subject to federal, state and local laws and regulations governing the use,
manufacture, storage, handling and disposal of such materials and certain waste
products. Although the Company believes that its activities currently comply
with the standards prescribed by such laws and regulations, the risk of
accidental contamination or injury from these materials cannot be eliminated.
In the event of such an accident, the Company could be held liable for any
damages that result and any such liability could exceed the resources of the
Company. In addition, there can be no assurance that the Company will not be
required to incur significant costs to comply with environmental laws and
regulations in the future.

POSSIBLE VOLATILITY OF STOCK PRICE

The market prices for securities of life sciences companies, including
the Company, have been highly volatile and the market has experienced
significant price and volume fluctuations that are unrelated to the operating
performance of particular companies. Announcements of technological
innovations or new commercial products by the Company or its competitors,
developments concerning proprietary rights, including patents and litigation
matters, publicity regarding actual or potential clinical trial results with
respect to products under development by the Company or others, decisions
regarding regulatory approvals of the products of the Company or others,
regulatory developments in both the United States and foreign countries, public
concern as to the efficacy of new technologies, general market conditions, as
well as quarterly fluctuations in the Company's revenues and financial results
and other factors, may have a significant impact on the market price of the
Common Stock. In particular,

-8-
<PAGE> 10
the realization of any of the risks described in these "Risk Factors" could
have a dramatic and adverse impact on such market price.

LARGE NUMBER OF SHARES ELIGIBLE FOR FUTURE SALE; EFFECT ON ABILITY TO RAISE
CAPITAL

Sales of substantial amounts of Common Stock in the public market
following this Offering could adversely affect the prevailing market price of
the Company's Common Stock and may have a material and adverse effect on the
Company's ability to raise the capital necessary to fund its future operations.
As of February 25, 1997, without taking into account shares of Common Stock
issued upon exercise of stock options, warrants or other rights to acquire
Common Stock after February 25, 1997, the Company had outstanding 25,077,970
shares of Common Stock. The Shares and substantially all of the shares of
Common Stock already outstanding, will be freely tradeable in the public market
without restriction under the Securities Act, except that any shares held by
"affiliates" of the Company, as such term is defined in Rule 144(a) under the
Securities Act ("Affiliates"), may generally only be sold in compliance with
the applicable provisions of Rule 144 of the Securities Act. In general, under
Rule 144 an Affiliate is entitled to sell within any three-month period a
number of shares that does not exceed the greater of 1% of the then outstanding
shares of the Company's Common Stock (approximately 250,779 shares) or the
average weekly trading volume in the Company's Common Stock on the American
Stock Exchange during the four calendar weeks preceding the date on which
notice of such sale was filed under Rule 144. Sales under Rule 144 are also
subject to certain provisions relating to the manner and notice of sale and the
availability of current public information about the Company. Additional
shares of Common Stock, including shares issuable upon exercise of options,
warrants and other rights to acquire Common Stock, will also become eligible
for sale in the public market from time to time in the future. Furthermore,
certain holders of Common Stock have the right to cause the Company to register
their shares under the Securities Act in the future. The Company is required
to bear the expenses of all such required registrations (except underwriting
discounts and commissions). The Company is required to use its best efforts to
effect such registrations, subject to certain conditions and limitations.

DIVIDENDS UNLIKELY

The Company has never paid any cash dividends on its Common Stock and
does not anticipate paying any cash dividends in the foreseeable future.

-9-
<PAGE> 11

ISSUANCE OF THE SHARES AND USE OF PROCEEDS

The Shares are issuable upon the exercise of outstanding Warrants and
Options. The aggregate gross proceeds that the Company could receive on the
exercise of the outstanding Warrants and Options is $11,250,000. The Company
intends to use any net proceeds from the exercise of the Warrants and the
Options for general corporate purposes, including working capital.

SELLING STOCKHOLDERS

The following table sets forth the number of shares of Common Stock
beneficially owned by each of the Selling Stockholders as of February 25, 1997.
None of the Selling Stockholders has had a material relationship with the
Company within the past three years other than as a result of the ownership of
the Shares or other securities of the Company. The Shares offered by this
Prospectus may be offered from time to time by the Selling Stockholders. See
"Plan of Distribution."

<TABLE>
<CAPTION>
Beneficial Ownership
After Offering(3)
------------------------------
Number of Shares Number of Shares
Beneficially Owned Registered Number
Name of Selling Stockholder Prior to Offering(1)(2) for Sale Hereby of Shares Percent
--------------------------- ----------------------- --------------- -------------- ---------------
<S> <C> <C> <C> <C>
Halifax Fund, L.P. . . . . . . . . . . 2,577,348 2,451,585 125,763 *
Heracles Fund . . . . . . . . . . . . . 1,005,634 980,634 25,000 *
Angelo, Gordon & Co., L.P. . . . . . . 472,516(4) 49,032 31,230(5) --
Olympus Securities . . . . . . . . . . 490,317 490,317 -- --
Joseph A. Umbach . . . . . . . . . . . 245,158 245,158 -- --
Descartes Capital . . . . . . . . . . . 245,158 245,158 -- --
Raphael, L.P. . . . . . . . . . . . . . 59,538 49,032 10,506 *
GAM Arbitrage Investments, Inc. . . . . 64,756 49,032 15,724 *
A.G. Super Fund International
Partners, L.P. . . . . . . . . . . . 54,032 49,032 5,000 *
A.G. Superfund, L.P. . . . . . . . . . 49,032 49,032 -- --
Michaelangelo, L.P. . . . . . . . . . . 49,032 49,032 -- --
AGD, LLC . . . . . . . . . . . . . . . 49,032 49,032 -- --
Nutmeg Partners, L.P. . . . . . . . . . 49,032 49,032 -- --
Northern Trust Company, as Master
Trustee of the Teacher's Retirement
System of the State of Illinois . . . 49,032 49,032 -- --
PHS Patriot Fund, L.P. . . . . . . . . 24,515 24,515 -- --
PHS Bay Colony Fund, L.P. . . . . . . . 24,515 24,515 -- --
Kevin W. Pettersen . . . . . . . . . . 4,475 4,475 -- --
----------- ----------- ----------- ---------

TOTAL . . . . . . . . . . . . 5,089,638 4,907,645 181,993 *
============ ============ ============ ============
</TABLE>

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

* Less than one percent.

(1) Certain of the Selling Stockholders will be the beneficial owner of
this number of shares of Common Stock if, and when, each such Selling
Stockholder either converts certain of the Debentures into shares of
Common Stock or exercises its right to purchase the shares of Common
Stock pursuant to certain of the Warrants.

(2) The number of shares of Common Stock beneficially owned by each
Selling Stockholder prior to the Offering is based on the maximum
amount of Debenture Shares issuable upon conversion of the Debentures.

(3) The number of shares of Common Stock and the percentage of shares of
Common Stock beneficially owned by each Selling Stockholder after the
Offering are based on the assumption that all of the Selling
Stockholders will sell all of the Debenture Shares and Warrant Shares
registered for sale hereby. See "Plan of Distribution."

-10-
<PAGE> 12

(4) Includes 59,538 shares beneficially owned by Raphael, L.P., 54,032
shares beneficially owned by A.G. Super Fund International Partners,
L.P., 49,032 shares beneficially owned by A.G. Superfund L.P., 49,032
shares beneficially owned by Michaelangelo, L.P., 24,515 shares
beneficially owned by PHS Patriot Fund, L.P., 24,515 shares
beneficially owned by PHS Bay Colony Fund, L.P. and 49,032 shares
beneficially owned by Nutmeg Partners L.P. Angelo, Gordon & Co., L.P.
is the general partner of the aforementioned limited partnerships.
Also includes 49,032 shares beneficially owned by AGD, LLC a limited
liability company of which Angelo, Gordon & Co. is the managing
member. Includes 64,756 shares beneficially owned by GAM Arbitrage
Investments, Inc. and 49,032 shares beneficially owned by Northern
Trust Company, as Master Trustee of the Teacher's Retirement System of
the State of Illinois ("Northern Trust Company"). Angelo, Gordon &
Co., L.P. is the investment advisor for both GAM Arbitrage
Investments, Inc. and Northern Trust Company.

(5) Includes 10,506 shares beneficially owned by Raphael, L.P. subsequent
to the Offering, 15,724 shares beneficially owned by GAM Arbitrage
Investments, Inc. subsequent to the Offering and 5,000 shares
beneficially owned by A.G. SuperFund International Partners, L.P.
subsequent to the Offering.

Assuming the exercise of all the outstanding Warrants, the Shares
issuable upon the exercise of the Warrants will be acquired by the Selling
Stockholders at a purchase price per share of $5.00, subject to adjustment. The
Shares are being registered as a result of the contractual arrangement with the
Selling Stockholders. The Company has agreed to bear certain expenses (other
than underwriting discounts and selling commissions and fees and disbursements
of counsel and other advisors to the Selling Stockholders) in connection with
the registration of the Shares.

The sale of Shares by Affiliates must generally be in compliance
with the applicable provisions of Rule 144. The Company has agreed to prepare
and file such amendments and supplements to the Registration Statement as may
be necessary to keep this Registration Statement effective until the earlier of
December 30, 2001, until all of the Shares have been sold pursuant to the terms
hereof or the date on which the Shares are saleable pursuant to Rule 144(k)
promulgated under the Securities Act.

-11-
<PAGE> 13
PLAN OF DISTRIBUTION

The Shares offered hereby are being offered directly by the Selling
Stockholders. The Company will not receive any of the proceeds from the sale
of the Debenture Shares by the Selling Stockholders. The Company will receive
aggregate proceeds of up to $11,250,000 upon the exercise of the Warrants and
the Options. The sale of the Shares may be effected by the Selling
Stockholders from time to time in transactions on the American Stock Exchange,
in negotiated transactions, or a combination of such methods of sale, at fixed
prices which may be changed, at market prices prevailing at the time of sale,
at prices related to prevailing market prices or at negotiated prices. The
Selling Stockholders may effect such transactions by selling the Shares to or
through broker-dealers, and such broker-dealers may receive compensation in the
form of discounts, concessions or commissions from the Selling Stockholders
and/or the purchasers of the Shares for whom such broker-dealers may act as
agents or to whom they sell as principals, or both (which compensation as to a
particular broker-dealer might be in excess of customary commissions). In
order to comply with the securities laws of certain states, if applicable, the
Shares will be sold in such jurisdictions only through registered or licensed
brokers or dealers. The Selling Stockholders may transfer their Shares under
certain circumstances to other persons who may, in turn, resell Shares in the
manner described above. In addition, the Selling Stockholders may pledge or
make gifts of their Shares and such Shares may also be sold by the pledgees or
transferees.

At the time a particular offer of Shares is made, to the extent
required, a Prospectus Supplement will be distributed which will set forth the
number of Shares being offered and the terms of the offering including the name
or names of any underwriters, dealers or agents, the purchase price paid by any
underwriter for the Shares purchased from Selling Stockholders, any discounts,
commissions and other items constituting compensation from the Selling
Stockholders and any discounts, commissions or concessions allowed or reallowed
or paid to dealers.

In order to comply with the securities laws of certain states, if
applicable, the Shares will be sold in such jurisdictions only through
registered or licensed brokers or dealers. In addition, in certain states the
Shares may not be sold unless they have been registered or qualified for sale
in the applicable state or an exemption from the registration or qualification
requirement is available and is complied with by the Company and the Selling
Stockholders.

The Selling Stockholders may also transfer their Shares pursuant to
Rule 144, whether or not the Registration Statement, of which this Prospectus
forms a part, is effective at the time of any such transfer.

The Selling Stockholders and any broker-dealers, agents or
underwriters that participate with the Selling Stockholders in the distribution
of the Shares may be deemed to be "underwriters" within the meaning of Section
2(11) of the Securities Act, and any commissions received by them and any
profit on the resale of the Selling Stockholder Shares purchased by them may be
deemed to be underwriting commissions or discounts under the Securities Act.
The Company has agreed to indemnify the Selling Stockholders and their
affiliates against certain liabilities, including liabilities under the
Securities Act. The Selling Stockholders have agreed to indemnify the Company
and its affiliates against certain liabilities, including liabilities under the
Securities Act.

Under applicable rules and regulations under the Exchange Act, any
person engaged in the distribution of the Shares may not simultaneously engage
in market making activities with respect to the Common Stock of the Company for
a period of two business days prior to the commencement of such distribution.
In addition and without limiting the foregoing, each Selling Stockholder will
be subject to applicable provisions of the Exchange Act and the rules and
regulations thereunder, including, without limitation, Rules 10b-6 and 10b-7,
which provisions may limit the timing of purchases and sales of shares of the
Company's Common Stock by the Selling Stockholders.

The Company has agreed to bear certain expenses (other than
underwriting discounts and selling commissions and fees and disbursements of
counsel and other advisors to the Selling Stockholders) in connection with the
registration of the Shares.

-12-
<PAGE> 14
LEGAL MATTERS

The validity of the Shares offered hereby will be passed upon for the
Company by Brobeck, Phleger & Harrison LLP, New York, New York.

EXPERTS

The financial statements of the Company incorporated in this
Prospectus by reference to the Company's 1995 Form 10-K, have been audited by
Arthur Andersen LLP, independent public accountants, as indicated in their
reports with respect thereto, and are included herein in reliance upon the
authority of said firm as experts in giving said reports.

-13-
<PAGE> 15

4,907,645

ONCOR, INC.

COMMON STOCK

PROSPECTUS

FEBRUARY 28, 1997

<PAGE> 16
PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 14. OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION

The following table sets forth an estimate of the expenses to be
incurred by the Company in connection with the issuance and distribution of the
securities being registered:
<TABLE>
<CAPTION>
Amount to
Be Paid
-----------
<S> <C>

Registration Fee - SEC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $ 6,082
Amex Listing Fee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17,500
Legal Fees and Expenses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20,000
Accounting Fees and Expenses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,500
Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12,813
----------
Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $ 58,895
==========
</TABLE>

ITEM 15. INDEMNIFICATION OF DIRECTORS AND OFFICERS

Article 11 of the Registrant's Articles of Incorporation, as amended,
and Section 5-01 of the Registrant's By-Laws, as amended, provide that the
Registrant shall, to the full extent permitted by law, indemnify all directors,
officers, employees or agents of the Registrant. Section 2-418 of the Maryland
General Corporation Law permits indemnification of directors, officers,
employees, and agents of a corporation under certain conditions and subject to
certain limitations. The Section provides generally that such persons may be
indemnified unless they engage in a material act or omission in bad faith or
that is the result of active and deliberate dishonesty, they actually receive
an improper personal benefit in money, property or services, or, in the case of
a criminal proceeding, they have reasonable cause to believe that the act or
omission is unlawful. Provision is made for reimbursement of reasonable
expenses so long as it is finally determined that the standards of conduct have
been met. The Selling Stockholders have agreed to indemnify officers,
directors and controlling persons of the Registrant against certain
liabilities, including liabilities under the Securities Act under certain
circumstances.

The Company and its directors and officers have liability insurance.

ITEM 16. EXHIBITS

The following is a list of Exhibits filed as part of the Registration
Statement:

4.1 Specimen certificate for shares of the Registrant's Common Stock,
incorporated herein by reference to Exhibit 4.1 to Registration
Statement No. 33-44520.

4.2 Provisions of the Articles of Incorporation and By-Laws of the
Registrant defining rights of holders of Common Stock of the
Registrant, incorporated herein by reference to Exhibits 3.1 and 3.2
to Registration Statement No. 33-44520.

4.3+ Form of 6% Convertible Debenture due December 30, 2001.

4.4+ Form of Common Stock Purchase Warrant.

5. Opinion of Brobeck, Phleger & Harrison LLP.

10.1+ Form of Subscription Agreement, Dated December 30, 1996.

23.1 Consent of Arthur Andersen LLP, independent public accountants.

II-1
<PAGE> 17

23.2 Consent of Brobeck, Phleger & Harrison LLP (included in the opinion
filed as Exhibit 5).

24.* Powers of Attorney.

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

* Previously filed.

+ Refiled pursuant to Rule 406 under the Securities Act of 1933, as amended.

ITEM 17. UNDERTAKINGS

Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the Registrant pursuant to the foregoing provisions, 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 Act, and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than 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 such director, officer or controlling person in connection with the
securities being registered, the Registrant will, unless in the opinion of its
counsel the matter has been settled by controlling precedent, submit to a court
of appropriate jurisdiction the question whether such indemnification by it is
against public policy as expressed in the Act and will be governed by the final
adjudication of such issue.

The undersigned Registrant hereby undertakes:

(1) To file, during any period in which offers or sales are being
made, a post-effective amendment to this registration statement;

(i) To include any prospectus required by Section
10(a)(3) of the Securities Act of 1933;

(ii) To reflect in the prospectus any facts or events
arising after the effective date of the registration statement
(or the most recent post-effective amendment thereof) which,
individually or in the aggregate, represent a fundamental change in
the information set forth in the registration statement.
Notwithstanding the foregoing, any increase or decrease in volume of
securities offered (if the total dollar value of securities offered
would not exceed that which was registered) and any deviation from the
low or high end of the estimated maximum offering range may be
reflected in the form of prospectus filed with the Commission pursuant
to Rule 424(b) if, in the aggregate, the changes in volume and price
represent no more than a 20 percent change in the maximum aggregate
offering price set forth in the "Calculation of Registration Fee"
table in the effective registration statement;

(iii) To include any material information with respect
to the plan of distribution not previously disclosed in the
registration statement or any material change to such information in
the registration statement;

(2) That, for the purpose of determining any liability under the
Securities Act of 1933, each such post-effective amendment 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.

(3) To remove from registration by means of a post-effective
amendment any of the securities being registered which remain unsold at the
termination of the offering.

The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act of 1933, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Securities Exchange Act of 1934 that is incorporated by reference in the
registration statement shall be deemed

II-2
<PAGE> 18
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.

The undersigned Registrant hereby undertakes that:

(1) For purposes of determining any liability under the Securities
Act of 1933, 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-3
<PAGE> 19
SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as
amended, the Registrant certifies that it has reasonable grounds to believe
that it meets all of the requirements for filing on Form S-3 and has duly
caused this Amendment No. 1 to the Registration Statement to be signed on its
behalf by the undersigned, thereunto duly authorized, in the City of
Gaithersburg, State of Maryland, on February 27, 1997.

ONCOR, INC.

By: /S/ Stephen Turner
-----------------------------------------
Stephen Turner, Chairman of the Board of
Directors and Chief Executive Officer

Pursuant to the requirements of the Securities Act of 1933, as
amended, this Amendment No. 1 to the Registration Statement has been signed by
the following persons in the capacities indicated on February 27, 1997.

<TABLE>
<CAPTION>
SIGNATURE TITLE
--------- -----
<S> <C>
/S/ Stephen Turner
- ------------------------------------------------------
Stephen Turner Chairman of the Board of Directors and Chief
Executive Officer (Principal Executive Officer)

*
- ------------------------------------------------------
John L. Coker Vice President -- Finance and Administration and
Chief Financial Officer (Principal Financial and
Accounting Officer)

*
- ------------------------------------------------------
Cecil Kost President, Chief Operating Officer and Director

*
- ------------------------------------------------------
Glenn W. Bartlett Director

*
- ------------------------------------------------------
Jose J. Coronas Director

*
- ------------------------------------------------------
Derace Lee Schaffer, M.D. Director

*
- ------------------------------------------------------
Philip S. Schein Director

*
- ------------------------------------------------------
William H. Taylor II Director

*
- ------------------------------------------------------
Timothy J. Triche, M.D., Ph.D. Director

*By: /S/ Stephen Turner
Stephen Turner
Attorney-in-Fact
</TABLE>
<PAGE> 20
EXHIBIT INDEX

<TABLE>
<CAPTION>
EXHIBIT
NO. DESCRIPTION PAGE
- ------- ----------- ----
<S> <C>
4.1 Specimen certificate for shares of the Registrant's Common Stock, incorporated
herein by reference to Exhibit 4.1 to Registration Statement No. 33-44520 . . . . . . . . . . .

4.2 Provisions of the Articles of Incorporation and By-Laws of the Registrant
defining rights of holders of Common Stock of the Registrant, incorporated herein
by reference to Exhibits 3.1 and 3.2 to Registration Statement No. 33-44520 . . . . . . . . . .

4.3+ Form of 6% Convertible Debenture due December 30, 2001 . . . . . . . . . . . . . . . . . . . .

4.4+ Form of Common Stock Purchase Warrant . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5. Opinion of Brobeck, Phleger & Harrison LLP . . . . . . . . . . . . . . . . . . . . . . . . . .

10.1+ Form of Subscription Agreement, Dated December 30, 1996 . . . . . . . . . . . . . . . . . . . .

23.1 Consent of Arthur Andersen LLP, independent public accountants . . . . . . . . . . . . . . . .

23.2 Consent of Brobeck, Phleger & Harrison LLP (included in the opinion filed as
Exhibit 5) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

24.* Powers of Attorney . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
</TABLE>

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

* Previously filed.

+ Refiled pursuant to Rule 406 under the Securities Act of 1933, as amended.

<PAGE> 1

EXHIBIT 4.3

THESE SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF
1933 OR ANY STATE SECURITIES LAWS. THEY MAY NOT BE SOLD OR OFFERED
FOR SALE EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER
SAID ACT AND ANY APPLICABLE STATE SECURITIES LAWS OR AN APPLICABLE
EXEMPTION FROM SUCH REGISTRATION REQUIREMENTS.

NO. 1 $_______________

6% CONVERTIBLE DEBENTURE DUE DECEMBER 30, 2001

THIS CONVERTIBLE DEBENTURE ("Debenture") is one of a duly authorized
issue of Debentures of Oncor, Inc., a corporation duly organized and existing
under the laws of the State of Maryland and having its principal address at 209
Perry Parkway, Gaithersburg, Maryland 20877 (the "Company"), designated as its
6% Convertible Debentures Due December 30, 2001 (as such date may be extended
pursuant to Section 5(a)(ii) below) in an aggregate principal amount not
exceeding Ten Million U.S. Dollars (U.S. $10,000,000) (the "Debentures").

FOR VALUE RECEIVED, the Company promises to pay to
______________________, having an address at ______________________, the holder
hereof, or its order (the "Holder"), the principal sum of
______________________ United States Dollars (U.S. $_______) on December 30,
2001 (as adjusted from time to time as provided herein and in the Registration
Rights Agreement, the "Maturity Date") and to pay interest on the principal sum
outstanding under this Debenture ("Outstanding Principal Amount"), at the rate
of 6% per annum due and payable semi-annually in arrears on the 30th day of
June and December of each year (each an "Interest Payment Date"), with the
first such payment due on June 30, 1997. Accrual of interest shall commence on
the first business day to occur after the date hereof and shall continue until
payment in full of the principal sum has been made. The interest so payable
will be paid to the person in whose name this Debenture is registered on the
records of the Company regarding registration and transfers of the Debentures
(the "Debenture Register"); provided, however, that the Company's obligation to
a transferee of this Debenture arises only if the transfer, sale or other
disposition is made in accordance with the terms and conditions of the
Subscription Agreement, dated as of December 30, 1996, between the Company and
the Holder (as amended from time to time and in effect, the "Subscription
Agreement"). The principal of and interest on this Debenture are
<PAGE> 2
- 2 -

payable in United States Dollars at the address last appearing on the Debenture
Register of the Company as designated in writing by the Holder hereof from time
to time; provided, however, that, in lieu of paying such interest in United
States Dollars, the Company may, at its option, pay interest on this Debenture
for any Interest Payment Date by adding the amount of such interest to the
Outstanding Principal Amount due under this Debenture ("PIK Interest") pursuant
to a statement in the form of Exhibit A hereto ("PIK Statement") delivered by
the Company to the Holder on or prior to the applicable Interest Payment Date.
If the cash interest due hereunder is not paid to the Holder by the applicable
Interest Payment Date, then the Holder shall be entitled to the addition of PIK
Interest hereunder and to the delivery of a PIK Statement with respect thereto.
Any PIK Interest when so added to the Outstanding Principal Amount due under
this Debenture shall, for all purposes of this Debenture, be deemed to have
been part of the principal indebtedness originally evidenced by this Debenture
including, without limitation, for purposes of determining interest thereafter
payable hereunder and amounts thereafter convertible into Common Stock
hereunder. Subject to the conversion hereof, in whole or in part, on or before
the Maturity Date pursuant to Paragraph 5 hereof, the Company will pay the
principal of and all accrued and unpaid interest due upon this Debenture on the
Maturity Date, to the Holder of this Debenture as of the tenth (10th) day prior
to the Maturity Date and addressed to such Holder at the last address appearing
on the Debenture Register.

This Debenture is subject to the following additional provisions:

1. Exchange. The Debentures are exchangeable for an equal
aggregate principal amount of Debentures of different denominations, of not
less than $50,000 (or the total principal amount, if less than $50,000) each as
requested by the Holder surrendering the same. No service charge will be made
for such exchange.

2. Transfers. This Debenture has been issued subject to
investment representations of the original purchaser hereof and may be
transferred or exchanged in the United States only in compliance with the
Securities Act of 1933, as amended (the "Act") and applicable state securities
laws and in accordance with other applicable provisions hereof. Prior to due
presentment for transfer of this Debenture, the Company may treat the person in
whose name this Debenture is duly registered on the Company's Debenture
Register as the owner hereof for the purpose of receiving payment as herein
provided and all other purposes, whether or not this Debenture is then overdue,
and the Company shall not be affected by notice to the contrary.

3. Definitions. For purposes hereof, the following terms shall
have the following meanings:
<PAGE> 3
- 3 -

"Closing Date" shall mean the date of original issuance of
this Debenture.

"Common Stock" shall mean the Common Stock, par value $.01 per
share, of the Company.

"Conversion Date Market Price" shall mean, at any Holder
Conversion Date, the lesser of (i) an amount that is equal to the percentage
set forth in the table below (the "Applicable Percentage") opposite the period
in which the Holder Conversion Date shall have occurred of the average Market
Price for Shares of Common Stock for the five trading days immediately
preceding the Holder Conversion Date, subject to adjustment as set forth in
Section 6 of the Registration Rights Agreement, (ii) the Maximum Conversion
Price.

<TABLE>
<CAPTION>
Holder Conversion Date Applicable Percentage
---------------------- ---------------------
<S> <C>
0 to 60 days after Closing Date 100%
61 to 90 days after Closing Date 85%
91 to 120 days after Closing Date 82.5%
121 days or more after Closing Date 80%
</TABLE>

"Conversion Deficiency" shall have the meaning set forth in
Paragraph 9(b).

"Conversion Notice" shall have the meaning set forth in
Paragraph 5(c).

"Conversion Rate" shall have the meaning set forth in
Paragraph 5(b).

"Equity Offerings" shall mean the issuance or sale by the
Company of any Common Stock or securities which are convertible into or
exchangeable for Common Stock, or any warrants or other rights to subscribe for
or to purchase, or any options for the purchase of, Common Stock or any such
convertible or exchangeable securities (other than shares or options issued or
which may be issued pursuant to the Company's employee or director option plans
or shares issued upon exercise of options, warrants or rights outstanding on
the Closing Date and listed in the Exchange Act Reports).

"Holder Conversion Date" shall have the meaning set forth in
Paragraph 5(c).

"Market Price for Shares of Common Stock" shall mean the price
of one share of Common Stock determined as follows:
<PAGE> 4
- 4 -

(i) If the Common Stock is listed on the
Exchange, the lowest sales price on the date of valuation, excluding any sales
made by the Holder or any affiliate of the Holder, as reported in the Wall
Street Journal; or

(ii) If the Common Stock is listed on any other
national securities exchange, the lowest sales price on the date of valuation,
excluding any sales made by the Holder or any affiliate of the Holder, as
reported in the Wall Street Journal; or

(iii) If neither (i) nor (ii) apply, but the Common
Stock is quoted in the over-the-counter market on the pink sheets or bulletin
board, the lowest sales price on the date of valuation, excluding any sales
made by the Holder or any affiliate of the Holder, as reported in the Wall
Street Journal; or

(iv) If none of clause (i), (ii) or (iii) above
applies, the market value as determined by an independent nationally recognized
investment banking firm or financial advisor retained in good faith by the
Company for such purpose, taking into consideration, among other factors, the
earnings history, book value and prospects for the Company, and the prices at
which shares of Common Stock recently have been traded. Such determination
shall be conclusive and binding on all persons.

"Maximum Conversion Price" shall mean Five United States
Dollars ($5.00) per share of Common Stock, subject to adjustment in Section 6
of the Registration Rights Agreement. Each time the Conversion Date Market
Price is reduced pursuant to Section 9 of the Registration Rights Agreement or
Paragraph 7 hereof, such reduced price shall become the Maximum Conversion
Price for all purposes of this Debenture.

"Paragraph 4 Transaction" shall mean a merger, consolidation,
or other transaction referred to in Paragraph 4.

"Redemption Date" shall have the meaning set forth in
Paragraph 6(c).

"Registration Rights Agreement" shall have the meaning set
forth in the Subscription Agreement.

"Subscription Agreement" shall mean the Subscription
Agreement, dated December 30, 1996, between the Company and the Subscriber to
the original issue of the Debentures and the Warrants, as such Subscription
Agreement may be amended from time to time.

"Warrants" shall have the meaning set forth in the
Subscription Agreement.
<PAGE> 5
- 5 -

Other terms defined in the Subscription Agreement and not
otherwise defined herein shall have the same meanings herein as are set forth
for such terms in the Subscription Agreement.

4. Merger; Consolidation. If at any time there occurs any
consolidation or merger of the Company with or into any other corporation or
other entity or person (whether or not the Company is the surviving
corporation) or any other corporate reorganization or similar transaction or
series of related transactions in which greater than 50% of the Company's
voting power is transferred (a "Paragraph 4 Transaction"), the Holder of this
Debenture, to the extent then outstanding shall participate in any such
transaction as a class with common stockholders of the Company on the same
basis as if this Debenture had been converted one day prior to the record date
or effective date of such Paragraph 4 Transaction; provided, however, that if a
Paragraph 4 Transaction or the record date for determination of the Company's
stockholders entitled to participate in such Paragraph 4 Transaction shall
occur at any time before the first anniversary of the effectiveness of the
Registration Statement contemplated by the Registration Rights Agreement, then,
at the option of the Holder of this Debenture, such Holder may treat the
effective date of such Paragraph 4 Transaction as a Redemption Date and shall
be entitled to receive the redemption price with respect to such Redemption
Date as is provided in Paragraph 6. Such Holder shall be entitled to make such
election at any time up to ten (10) trading days after the closing date of the
Paragraph 4 Transaction. Nothing in this Section 4 shall prohibit the Holder
from converting any part or all of this Debenture in accordance with the terms
hereof, up to and including the closing date of the Paragraph 4 Transaction.

5. Conversion. This Debenture is subject to conversion as
follows:

(a) (i) Holder's Right to Convert. This Debenture shall
be convertible at any time and from time to time, in whole or in part, but not
in an amount less than $50,000 of the Outstanding Principal Amount of this
Debenture (unless such amount represents the entire Outstanding Principal
Amount), at the option of the Holder hereof, into fully paid, validly issued
and nonassessable shares of Common Stock.

(ii) Automatic Conversion. At maturity of this
Debenture, the principal indebtedness then outstanding hereunder (including
without limitation all PIK Interest then included therein) shall automatically
be converted into fully paid, validly issued and nonassessable shares of Common
Stock and, except for the Holder's right to receive the Common Stock into which
this Debenture is automatically so converted, this Debenture shall be deemed to
have been canceled whether or not surrendered upon such automatic conversion.
The maturity date set forth on the face page of this Debenture shall be
extended by that number of days
<PAGE> 6
- 6 -

equal to twice the number of days for which the Holder shall be subject to any
market stand-off pursuant to Section 9 of the Registration Rights Agreement

(iii) Accrued But Unpaid Interest. Notwithstanding
anything in this Debenture to the contrary, the Outstanding Principal Amount of
this Debenture on any Holder Conversion Date shall include, without limitation,
all accrued but unpaid interest under this Debenture.

(b) Conversion Price for Holder Converted Shares. The
Outstanding Principal Amount of this Debenture that is converted into shares of
Common Stock shall be convertible into the number of shares of Common Stock
determined in accordance with the following formula:

P + I
--------------------------------
Conversion Date Market Price

P = principal amount of this Debenture submitted for
conversion
I = accrued but unpaid interest on the principal amount of
this Debenture submitted for conversion as of the Holder
Conversion Date

The number of shares of Common Stock into which the Outstanding
Principal Amount of this Debenture, and interest accrued but unpaid thereon,
may be converted pursuant to this paragraph is hereafter referred to as the
"Conversion Rate."

(c) Mechanics of Conversion. In order to convert this
Debenture (in whole or in part) into full shares of Common Stock, the Holder
shall surrender this Debenture, duly endorsed, by either overnight courier or
2-day courier, to the Company, and, in case of any conversion pursuant to
Section 5(a)(i), shall give written notice in the form of Exhibit B hereto (the
"Conversion Notice") by facsimile (with the original of such notice forwarded
with the foregoing courier) to the Company that the Holder elects to convert
the principal amount of this Debenture specified therein, which notice and
election shall be irrevocable by the Holder; provided, however, that the
Company shall not be obligated to issue certificates evidencing the shares of
the Common Stock issuable upon conversion unless (i) this Debenture evidencing
the principal amount of this Debenture to be converted is delivered to the
Company as provided above, or the Holder notifies the Company that this
Debenture has been lost, stolen or destroyed and promptly executes an agreement
reasonably satisfactory to the Company to indemnify the Company from any loss
incurred by it in connection with this Debenture, and (ii) the Company is
provided with a replacement Debenture which represents the portion of the
principal amount of this Debenture which is not being submitted for conversion;
and provided, further,
<PAGE> 7
- 7 -

that each Conversion Notice shall provide for the Holder's election to convert
either (A) at least $50,000 of the Outstanding Principal Amount of this
Debenture, or (B) if such Outstanding Principal Amount shall then be less than
$50,000, the entire Outstanding Principal Amount.

Upon receipt of any Conversion Notice, the Company
shall immediately verify the Holder's calculation of the Conversion Rate. In
the case of any Conversion Notice given by the Holder or in the case of
automatic conversion pursuant to Paragraph 5(a)(ii), the Company shall use its
best efforts to issue and deliver within two (2) business days after delivery
to the Company of the Debenture, or after receipt of such agreement and
indemnification, to such Holder or to its designee, a certificate or
certificates for the number of shares of Common Stock to which the Holder shall
be entitled, together with a Debenture for the principal amount not submitted
for conversion, the form of which shall have been provided to the Company prior
to the Company's delivery of a certificate or certificates for the number of
shares of Common Stock to which the Holder shall be entitled. The date on
which the Conversion Notice is given (the "Holder Conversion Date") shall be
deemed to be the date the Company received by facsimile the Conversion Notice.
The person or persons entitled to receive the shares of Common Stock issuable
upon conversion shall be treated for all purposes as the record holder or
holders of such shares of Common Stock on the Holder Conversion Date or on the
Maturity Date, as the case may be.

(d) Limitations on Conversion. In connection with a
conversion of this Debenture effected pursuant to the terms of this Section 5,
in no event shall the Company issue to the Holder more than that number of
shares of Common Stock which, together with the Common Stock (i) theretofore
issued upon conversion of Debentures (including Additional Shares) and exercise
of Warrants and (ii) reserved for issuance upon exercise of then unexercised
Warrants, would exceed 4,761,230 shares of Common Stock, as such number is
adjusted from time to time pursuant to the provisions hereof (the "Maximum
Share Amount"). Once the Maximum Share Amount has been issued, the remaining
Outstanding Principal Amount shall be immediately due and payable by the
Company to the Holder in immediately available funds at an amount equal to the
Redemption Price.

(e) (i) Additional Shares of Common Stock. In
connection with a conversion of any Debenture in the aggregate principal amount
of $50,000 or greater effected pursuant to the terms of this Paragraph 5, if
the Conversion Date Market Price shall be equal to or greater than $4.00 (the
"Minimum Additional Share Price"), subject to adjustment from time to time as
set forth in Paragraph 7 hereof, then, in addition to and not in lieu of the
shares of Common Stock issuable by reason of any Conversion Notice given by the
Holder on such Holder Conversion Date or by reason of automatic conversion
pursuant to Paragraph 5(a)(ii), such Holder may, by written notice to the
Company on the Holder Conversion Date, purchase from the
<PAGE> 8
- 8 -

Company, at a price per share equal to the Conversion Date Market Price, up to
one (1) share of Common Stock (each an "Additional Share" and, collectively,
with all such other shares so purchased and sold hereunder, "Additional
Shares") for each share of Common Stock issuable to such holder by reason of
any Conversion Notice given by the Holder on such Holder Conversion Date or by
reason of automatic conversion pursuant to Paragraph 5(a)(ii), and failure to
exercise the right to purchase Additional Shares on the Holder Conversion Date
shall result in forfeiture of such right. The total price for such Additional
Shares so to be issued incident to such a Conversion Notice or automatic
conversion shall be paid by such Holder by wire transfer of immediately
available federal funds to such account as the Company shall specify in writing
to such Holder, and upon receipt of such payment, the Company shall promptly
and in no event later than two (2) days issue the certificate or certificates
therefor pursuant to this Paragraph 5 hereof.

(ii) Second Warrant. On any date the Holder
purchases Additional Shares pursuant to Paragraph 5(e)(i), the Holder shall
receive a Common Stock purchase warrant, in the form attached hereto as Exhibit
C (the "Second Warrant"), exercisable for an additional number of shares of
Common Stock equal to the aggregate purchase price of Additional Shares paid by
the Holder on such date, divided by $40.00, at an exercise price equal to 135%
of the average Market Price for Shares of Common Stock for the five trading
days immediately preceding the Holder Conversion Date.

6. Redemption. The Company shall have the following redemption
obligations.

(a) Company's Obligation To Redeem. Any portion of this
Debenture which, at any time on or before the Maturity Date, shall become
eligible for redemption under any provision of this Agreement shall, at the
Holder's option expressed by notification to the Company (a "Redemption
Notice"), be redeemed by the Company in accordance with this Section 6.

(b) Redemption Price. The redemption price for the
portion of this Debenture being redeemed shall equal the greater of (i) the
closing market price on the Exchange on the day on which the Redemption Notice
was delivered to the Company, multiplied by the number of shares into which
such portion of this Debenture could have been converted on such day pursuant
to Section 5, and (ii) 110% of the Outstanding Principal Amount of this
Debenture being so redeemed, plus accrued but unpaid interest on such amount to
the date of redemption (such greater price being referred to as the "Redemption
Price").

(c) Mechanics of Redemption. In the event the Company
shall be required to redeem any part or all of the Outstanding Principal Amount
of the Debentures, the Company shall send by either overnight courier or 2-day
courier
<PAGE> 9
- 9 -

(with a copy sent by facsimile) notice of such determination to the record
Holders of the Debentures being redeemed (the "Redemption Debentures"). If the
Company shall not have the funds available to pay the aggregate Redemption
Price of all Redemption Debentures, then, without limiting the Company's
obligation to redeem all Redemption Debentures, such redemption shall be made
from each Holder, pro rata according to the portion of the total Outstanding
Principal Amount of all Redemption Debentures then held by each Holder. The
notice shall provide that the redemption shall occur on a date (the "Redemption
Date") that is no later than seven (7) business days after the date such notice
was sent by confirmed facsimile to such record Holders. On the Redemption Date
the Redemption Debentures shall be redeemed automatically without any further
action by the Holders of such Debentures and whether or not the Debentures are
surrendered to the Company; provided, that the Company shall be obligated to
pay the cash consideration due to a Holder of such Debentures upon redemption
when such Debentures are either delivered to the principal office of the
Company or the Holder notifies the Company that such Debentures have been lost,
stolen or destroyed and executes an agreement reasonably satisfactory to the
Company to indemnify the Company from any loss incurred by it in connection
with such Debenture. Thereupon, there shall be promptly issued and delivered
to such Holder, within seven (7) business days after the Redemption Date and
delivery to the Company of such Debentures, or after receipt of such agreement
and indemnification, at the address of such Holder on the books of the Company,
payment in immediately available funds to the name as shown on the books of the
Company in the amount of the redemption price as calculated as set forth in
Paragraph 6(b).

(d) Suspension of Redemption. If the Company is unable to pay the
aggregate Redemption Price for any redemption of Debentures required by Section
5(d), the Company may, by notice to the Holder, suspend such redemption for a
period of up to 60 days if the Company (i) decides to seek approval of its
stockholders of the issuance of such additional number of shares of its Common
Stock as will enable full conversion of all the Debentures into Common Stock at
all times on or before the Maturity Date in accordance with the terms thereof,
(ii) pursues such approval with all due diligence during such suspension and
(iii) obtains such approval within such 60 days. Upon receipt of such
approval, the Company will notify the Holder. Thereafter, the Company will,
upon the request of the Holder, either (i) immediately cause to be delivered to
the Holder the greater of (A) the number of shares of Common Stock issuable
upon conversion of the outstanding portion of the Debentures as if converted on
the original conversion date, (B) the number of shares of Common Stock
issuable upon conversion of the outstanding portion of the Debentures as of the
date of such approval, or (ii) return the Debenture to the Holder.

7. Stock Splits: Dividends, Adjustments, Reorganizations.
<PAGE> 10
- 10 -

(a) Stock Splits and Combinations. The Company shall not
effect or fix a record date for any stock split, subdivision or combination
with an effective date within five (5) trading days of a Redemption Date, the
receipt of a Conversion Notice, or the effective date of a Paragraph 4
Transaction.

(b) Certain Dividends and Distributions. The Company
shall not make, or fix a record date for the determination of holders of Common
Stock entitled to receive, a dividend or other distribution payable in
additional shares of Common Stock, with an effective date within five (5)
trading days of a Redemption Date, the receipt of a Conversion Notice, or the
effective date of a Paragraph 4 Transaction.

(c) Subdivisions, Combinations, etc. If the Company
shall subdivide its outstanding Common Stock, by split-up, spin-off, or
otherwise, or combine its outstanding Common Stock, then the Conversion Rate in
effect as of the date of such subdivision, split-up, spin-off or combination
shall forthwith be proportionately adjusted.

(d) Adjustment for Dividends and Distributions. In the
event the Company at any time or from time to time after the Closing Date
makes, or fixes a record date for the determination of holders of Common Stock
entitled to receive, a dividend or other distribution payable in securities of
the Company other than shares of Common Stock (including, without limitation,
rights to acquire Common Stock or such other securities), then and in each such
event provision shall be made so that the Holders of Debentures shall receive
upon conversion thereof pursuant to Paragraph 5 hereof, in addition to the
number of shares of Common Stock receivable thereupon, the amount of such other
securities of the Company to which a Holder on the relevant record or payment
date, as applicable, of the number of shares of Common Stock so receivable upon
conversion would have been entitled, plus any dividends or other distributions
which would have been received with respect to such securities, had such Holder
thereafter, during the period from the date of such event to and including the
Holder Conversion Date, retained such securities, subject to all other
adjustments called for during such period under this Paragraph 7 with respect
to the rights of the Holders of the Debentures. For purposes of this Paragraph
7(d), the number of shares of Common Stock so receivable upon conversion by the
Holder shall be deemed to be that number which the Holder would have received
upon conversion of the entire Outstanding Principal Amount hereof if the Holder
Conversion Date had been the day preceding the date upon which the Company
announced the making of such dividend or other distribution.

(e) Adjustment for Merger, Reorganization; etc. In the
event that at any time or from time to time after the Closing Date, the Common
Stock issuable upon conversion of the Debentures is changed into the same or a
different number of shares of any class or classes of stock, whether in
connection with a merger or consolidation, by recapitalization,
reclassification, reorganization or otherwise (other
<PAGE> 11
- 11 -

than a subdivision or combination of shares or stock dividend or reorganization
provided for elsewhere in this Paragraph 7 or a merger or consolidation
provided for in Paragraph 4), then and in each such event each Holder of
Debentures shall have the right thereafter to convert such Debenture into the
kind of securities receivable upon such merger, recapitalization,
reclassification or other change, all subject to further adjustment as provided
herein. In such event, the formulae set forth herein for conversion and
redemption shall be equitably adjusted to reflect such change in number of
shares or, if shares of a new class of stock are issued, to reflect the market
price of the class or classes of stock (applying the same factors used in
determining the Market Price for Shares of Common Stock) issued in connection
with the above described transaction.

(f) Conversion Price Adjustment. In the event that the
Company issues or sells any Common Stock or securities which are convertible
into or exchangeable for its Common Stock, or any warrants or other rights to
subscribe for or to purchase, or any options for the purchase of, its Common
Stock or any such convertible securities (other than issuance of the Warrants
and shares of Common Stock pursuant to the exercise thereof, shares or options
issued or which may be issued pursuant to the Company's employee or director
option plans or shares issued upon exercise of options, warrants or rights
outstanding on the Closing Date and listed in the Exchange Act Reports, but
including, without limitation, any such issuance in a Paragraph 4 Transaction)
at an effective purchase price per Common Share which is less than the
Conversion Date Market Price or the Minimum Additional Share Price, whichever
is lower, then the Conversion Date Market Price and the Minimum Additional
Share Price shall thereafter be equal to the lesser of (i) the lowest effective
purchase price per Common Share in such offering or sale, and (ii) the
Conversion Date Market Price or the Minimum Additional Share Price determined
as set forth in the definitions thereof. For purposes of the foregoing, the
amount of consideration received by the Company for any such issuance or sale,
other than cash, shall be the fair market value thereof as determined by the
Company's Board of Directors or, at the option of the Holders of Debentures
evidencing 50% or more of the principal indebtedness then evidenced thereby, by
an investment banker or other appraiser selected by such Holders and reasonably
acceptable to the Company.

(g) Disputes. In the event of a reasonable, good faith
dispute between a Holder of Debentures and the Company with respect to the
adjustments required by Paragraphs 7(c), (d), (e) or (f), then, at the option
of either the Holders of Debentures evidencing 50% or more of the principal
indebtedness evidenced by all Debentures held by Holders involved in such
dispute or the Company, the dispute shall be submitted to the American
Arbitration Association for resolution according to the then applicable rules
thereof. The cost of such proceeding shall be shared 50% by the Holder or
Holders involved in the dispute and 50% by the Company, except that each party
shall bear its own legal and other expenses.
<PAGE> 12
- 12 -

8. Fractional Shares. No fractional shares of Common Stock or
scrip representing fractional shares of Common Stock shall be issuable
hereunder. The number of shares of Common Stock that are issuable upon any
conversion shall be rounded up or down to the nearest whole share.

9. Reservation of Stock Issuable Upon Conversion.

(a) Reservation Requirement. The Company has reserved
and the Company shall continue to reserve and keep available at all times, free
of preemptive rights, shares of Common Stock for the purpose of enabling the
Company to satisfy any obligation to issue shares of its Common Stock upon
conversion of the Debentures (including the Additional Shares) or upon exercise
of Warrants; provided, however, that the number of shares so reserved shall at
all times be at least 4,761,230 shares, of which 250,000 shares shall be so
reserved, first, for issuance upon exercise of the First Warrants and, second,
for issuance upon conversion of Debentures (including Additional Shares) and
upon exercise of the Second Warrants if and to the extent the First Warrants
expire unexercised. The number of shares so reserved may be reduced by the
number of shares actually delivered pursuant to conversion of Debentures
(including the purchase of Additional Shares) and exercise of Warrants
(provided, that in no event shall the number of shares so reserved be less than
the maximum number required to satisfy remaining conversion rights on the
unconverted Debentures and remaining exercise rights under any Warrants) and
the number of shares so reserved shall be increased or decreased proportionally
to reflect stock splits, stock dividends, distributions or subdivisions or
combinations of Common Stock.

(b) Conversion Deficiency. If the Company does not have
a sufficient number of shares of Common Stock available to satisfy the
Company's obligations to a Holder of Debentures upon receipt of a Conversion
Notice or automatic conversion on the Maturity Date, each Holder of the
Debentures shall have the right to demand from the Company immediate redemption
of any portion of the Debentures with respect to which the Company does not
have a sufficient number of shares available to satisfy such conversation
obligations, in cash at the Redemption Price pursuant to Section 6 hereof.

10. No Impairment. The Company shall not intentionally take any
action which would impair the contractual rights and privileges of the
Debentures set forth herein or of the Holders thereof.

11. Holders' Rights if Shares are Delisted or if Trading in Common
Stock is Suspended. In the event that at any time on or after the date hereof
and prior to the fifth anniversary of the Closing Date, trading in the shares
of the Company's Common Stock is suspended on the Exchange for a period of five
consecutive trading
<PAGE> 13
- 13 -

days, other than as a result of the suspension of trading in securities in
general, or if such Shares are delisted and not relisted within twenty (20)
days thereafter, then, at a Holder's option, the Company shall redeem such
Holder's Debentures on a Redemption Date designated by such Holder, and at the
Redemption Price and in accordance with Section 6 hereof.

12. Limitations on Holder's Obligation to Convert.
Notwithstanding anything to the contrary contained herein, no Holder shall be
required to convert any part of this Debenture in excess of the portion then
convertible into that number of shares of Common Stock specified in the
Holder's representation to the Company that, after giving effect to the shares
of the Company's Common Stock to be issued pursuant to such Conversion Notice,
the total number of shares of Common Stock deemed beneficially owned by the
Holder, together with all shares of the Company's Common Stock deemed
beneficially owned by the Holder's "affiliates" as defined in Rule 144 of the
Act, would exceed 4.9% of the total issued and outstanding shares of the
Company's Common Stock.

13. Obligations Absolute. No provision of this Debenture, other
than conversion as provided herein, shall alter or impair the obligation of the
Company, which is absolute and unconditional, to pay the principal of, and
interest on, this Debenture at the time, place and rate, and in the manner,
herein prescribed.

14. Waivers of Demand, Etc. The Company hereby expressly waives
demand and presentment for payment, notice of nonpayment, protest, notice of
protest, notice of dishonor, notice of intent to accelerate, prior notice of
bringing of suit and diligence in taking any action to collect amounts called
for hereunder and will be directly and primarily liable for the payments of all
sums owing and to be owing hereon, regardless of and without any notice (except
as required by law), diligence, act or omission as or with respect to the
collection of any amount called for hereunder.

15. Replacement Debentures. In the event that the Holder notifies
the Company that its Debenture has been lost, stolen or destroyed, a
replacement Debenture identical in all respects to the original Debenture
(except for registration number and Outstanding Principal Amount, if different
than that shown on the original Debenture) shall be issued to the Holder,
provided that the Holder executes and delivers to the Company an agreement
reasonably satisfactory to the Company to indemnify the Company from any loss
incurred by it in connection with the Debenture and provided that the Company
is provided a form of Debenture for such replacement purposes.

16. Payment of Expenses. The Company agrees to pay all debts and
expenses, including reasonable attorneys' fees, which may be incurred by the
Holder
<PAGE> 14
- 14 -

in enforcing the provisions of this Debenture and/or collecting any amount due
under this Debenture, the Subscription Agreement or the Registration Rights
Agreement.

17. Defaults. If one or more of the following events (hereinafter
called "Events of Default") shall occur:

(a) The Company shall default in the payment (whether in
cash or by the issuance of a PIK Statement) of
interest on this Debenture, and such default shall
continue for five (5) business days after the due
date thereof; or

(b) Any of the representations or warranties made by the
Company herein, in the Subscription Agreement, or in
any certificate, financial statements or press
releases of the Company heretofore or hereafter
furnished by or on behalf of the Company in
connection with the execution and delivery of this
Debenture or the Subscription Agreement shall be
false or (when taken together with other information
furnished by or on behalf of the Company, including
Exchange Act Reports) misleading in any material
respect at the time made; or

(c) The Company shall fail to perform or observe any
covenant or agreement in the Subscription Agreement,
the Registration Rights Agreement or any of the
issued and outstanding Warrants, or any other
covenant, term, provision, condition, agreement or
obligation of the Company under this Debenture
(including without limitation any failure to make any
payments upon redemption of this Debenture and any
failure to issue shares of Common Stock, including
any Additional Shares, or the Second Warrants upon
conversion of this Debenture), and such failure shall
continue uncured for a period of ten (10) business
days after notice from the Holder of such failure; or

(d) The Company shall (i) become insolvent; (ii) admit in
writing its inability to pay its debts generally as
they mature; (iii) make a general assignment for the
benefit of creditors or commence proceedings for its
dissolution; or (iv) apply for or consent to the
appointment of a trustee, liquidator or receiver for
it or for a substantial part of its property or
business; or

(e) A trustee, liquidator or receiver shall be appointed
for the Company or for a substantial part of its
property or business without its consent and shall
not be discharged within forty-five (45) days after
such appointment; or
<PAGE> 15
- 15 -

(f) Any governmental agency or any court of competent
jurisdiction shall assume custody or control of the
whole or any substantial portion of the properties or
assets of the Company and shall not be dismissed
within forty-five (45) days thereafter, or

(g) Any money judgment, writ or warrant of attachment or
similar process in excess of Five Hundred Thousand
Dollars ($500,000) in the aggregate shall be entered
or filed against the Company or any of its properties
or other assets and shall remain unpaid, unvacated,
unbonded and unstayed for a period of forty-five (45)
days or in any event later than ten (10) days prior
to the date of any proposed sale thereunder; or

(h) Bankruptcy, reorganization, insolvency or liquidation
proceedings or other proceedings, or relief under any
bankruptcy law or any law for the relief of debt
shall be instituted by or against the Company and, if
instituted against the Company, shall not be
dismissed within forty-five (45) days after such
institution, or the Company shall by any action or
answer approve of, consent to, or acquiesce in any
such proceedings or admit to any material allegations
of, or default in answering a petition filed in, any
such proceeding;

then, or at any time thereafter prior to the date on which all continuing
Events of Default have been cured, and in each and every such case, unless such
Event of Default shall have been waived in writing by the Holder (which waiver
shall not be deemed to be a waiver of any subsequent default) at the option of
the Holder and in the Holder's sole discretion, the Holder may, by notice to
the Company declare this Debenture immediately due and payable, and the Holder
may immediately, and without expiration of any period of grace, enforce any and
all of the Holder's rights and remedies provided herein or any other rights or
remedies afforded by law. In such event, the Debenture shall be redeemed at a
redemption price per Debenture equal to the redemption price provided in
Paragraph 6(b).

18. Savings Clause. In case any provision of this Debenture is
held by a court of competent jurisdiction to be excessive in scope or otherwise
invalid or unenforceable, such provision shall be adjusted rather than voided,
if possible, so that it is enforceable to the maximum extent possible, and the
validity and enforceability of the remaining provisions of this Debenture will
not in any way be affected or impaired thereby.
<PAGE> 16
- 16 -

19. Entire Agreement. This Debenture and the agreements referred
to in this Debenture constitute the full and entire understanding and agreement
between the Company and the Holder with respect to the subject hereof. Neither
this Debenture nor any term hereof may be amended, waived, discharged or
terminated other than by a written instrument signed by the Company and a
majority-in-interest of the Holders.

20. Assignment, Etc. The Holder may, subject to compliance with
the Subscription Agreement, without notice, transfer or assign this Debenture
or any interest herein (but in no event in an amount less than $50,000 in
Outstanding Principal Amount or, if less than $50,000, the total Outstanding
Principal Amount hereof) and may mortgage, encumber or transfer any of its
rights or interest in and to this Debenture or any part hereof, and each
assignee, transferee and mortgagee (which may include any affiliate of the
Holder) shall have the right to so transfer or assign its interest; provided,
however, that (i) without the Company's consent, neither the Holder nor any
such assignee, transferee or mortgagee may transfer or assign this Debenture or
any part hereof to any direct competitor of the Company, and (ii) before the
Registration Statement contemplated by the Registration Rights Agreement
becomes effective, Holder will furnish the Company with an opinion of counsel
to the effect that such assignment, transfer, mortgage or other encumbrance is
exempt from the registration requirements under the Securities Act. Each such
assignee, transferee and mortgagee shall have all of the rights and obligations
of the Holder under this Debenture. The Company agrees that, subject to
compliance with the Subscription Agreement, after receipt by the Company of
written notice of assignment from the Holder or from the Holders' assignee, all
principal, interest, and other amounts which are then due and thereafter become
due under this Debenture shall be paid to such assignee at the place of payment
designated in such notice. This Debenture shall be binding upon the Company
and its successors and shall inure to the benefit of the Holder and its
successors and assigns.

21. No Waiver. No failure on the part of the Holder to exercise,
and no delay in exercising, any right, remedy or power hereunder shall operate
as a waiver thereof, nor shall any single or partial exercise by the Holder of
any right, remedy or power hereunder preclude any other or future exercise of
any other right, remedy or power. Each and every right, remedy or power hereby
granted to the Holder or allowed it by law or other agreement shall be
cumulative and not exclusive of any other, and may be exercised by the Holder
from time to time.

22. Miscellaneous. Unless otherwise provided herein, any notice
or other communication to a party hereunder shall be deemed to have been duly
given if personally delivered or sent by registered or certified mail, return
receipt requested, postage prepaid with a copy in each case sent on the same
day to the party by facsimile, Federal Express or other such expedited means to
said party at its address set forth herein or such other address as either may
designate for itself in such notice
<PAGE> 17
- 17 -

to the other and communications shall be deemed to have been received when
delivered personally or, if sent by mail or facsimile, when actually received
by the party to whom it is addressed. Whenever the sense of this Debenture
requires, words in the singular shall be deemed to include the plural and words
in the plural shall be deemed to include the singular. Paragraph headings are
for convenience only and shall not affect the meaning of this document.

23. Choice of Law and Venue: Waiver of Jury Trial. THIS
DEBENTURE SHALL BE CONSTRUED UNDER THE LAWS OF THE STATE OF NEW YORK, WITHOUT
REGARD TO PRINCIPLES OF CONFLICTS OF LAW OR CHOICE OF LAW. The Company hereby
(i) irrevocably submits to the exclusive jurisdiction of the United States
District Court for the Southern District of New York for the purposes of any
suit, action or proceeding arising out of or relating to this Debenture and
(ii) waives, and agrees not to assert in any such suit, action or proceeding,
any claim that it is not personally subject to the jurisdiction of such court,
that the suit, action or proceeding is brought in an inconvenient forum or that
the venue of the suit, action or proceeding is improper. The Company consents
to process being served in any such suit, action or proceeding by mailing a
copy thereof to the Company at the address in effect for notices to it under
this Debenture and agrees that such service shall constitute good and
sufficient service of process and notice thereof. Nothing in this paragraph
shall affect or limit any right to serve process in any other manner permitted
by law.
<PAGE> 18
- 18 -

IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed by an officer thereunto duly authorized.

Dated: December 30, 1996

ONCOR, INC.

By:
-------------------------------------
Name:
-----------------------------
Title:
----------------------------------
209 Perry Parkway
Gaithersburg, Maryland 20877

ATTEST:

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

<PAGE> 19

EXHIBIT C

Right to Purchase ___________ Shares of Common Stock of Oncor, Inc.

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

Common Stock Purchase Warrant

Oncor, Inc., a Maryland corporation having an address at 209 Perry
Parkway, Gaithersburg, Maryland 20877, (the "Company"), hereby certifies that
for Ten United States Dollars ($10.00) and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged,
___________________, having an address at __________________________________
("Purchaser") or any other Warrant Holder is entitled, on the terms and
conditions set forth below, to purchase from the Company at any time after the
date hereof and ending sixty (60) months after the date hereof
________________________ (________) shares of fully paid and nonassessable
shares of Common Stock, $.01 par value, of the Company (the "Common Stock"), at
the Purchase Price (hereinafter defined), as the same may be adjusted pursuant
to Section 5 herein.

1. Definitions.

(a) the term "Warrant" shall mean this Common Stock Purchase
Warrant, sometimes referred to in the Agreement as the First Warrant.

(b) the term "Warrant Holder" shall mean the Purchaser or any
assignee of all or any portion of this Warrant at any given time who, at the
time of assignment, acquired the right to purchase at least 1000 Warrant Shares
(such number being subject to adjustment after the date hereof pursuant to
Section 5 herein.)

(c) the term "Warrant Shares" shall mean the shares of Common
Stock or other securities issuable upon exercise of this Warrant.
<PAGE> 20
- 2 -

(d) the term "Purchase Price" shall mean Five United States
Dollars ($5.00) per share of Common Stock.

(e) the term "Act" shall mean the Securities Act of 1933, as
amended.

(f) the term "Exchange Act" shall mean the Securities and
Exchange Act of 1934, as amended.

(g) the term "SEC" or "Commission" shall mean the Securities
and Exchange Commission or any successor agency.

(h) the term "Rule 144" shall mean Rule 144 promulgated under
the Act, as amended, and any successor rules promulgated under the Act.

(i) other terms used herein which are defined in the
Subscription Agreement (the "Agreement") between the Company and the Purchaser
shall have the same meanings herein as therein.

2. Exercise of Warrant.

This Warrant may be exercised by the Warrant Holder, in whole or in
part, at any time and from time to time by surrender of this Warrant, together
with the form of subscription at the end hereof duly executed by the Warrant
Holder, and delivery of the Purchase Price for such Warrant Shares to the
Company, at the Company's principal office. In the event that the Warrant is
not exercised in full, the number of Warrant Shares shall be reduced by the
number of such Warrant Shares for which this Warrant is exercised, and the
Company, after receipt by it of a form of Warrant reflecting such adjusted
Warrant Shares, at its expense, shall forthwith issue and deliver to or upon
the order of the Warrant Holder a new Warrant of like tenor in the name of the
Warrant Holder or as the Warrant Holder (upon payment by the Warrant Holder of
any applicable transfer taxes) may request, reflecting such adjusted Warrant
Shares.

3. Delivery of Stock Certificates.

(a) Subject to the terms and conditions of this Warrant,
as soon as practicable after the exercise of this Warrant in full or in part,
and in any event within two (2) business days thereafter, the Company at its
expense (including, without limitation, the payment by it of any applicable
issue taxes) will cause to be issued in the name of and delivered to the
Warrant Holder, or as the Warrant Holder (upon payment by the Warrant Holder of
any applicable transfer taxes) may lawfully direct,
<PAGE> 21
- 3 -

a certificate or certificates for the number of fully paid and non-assessable
shares of Common Stock to which the Warrant Holder shall be entitled on such
exercise, together with any other stock or other securities or property
(including cash, where applicable) to which the Warrant Holder is entitled upon
such exercise.

(b) This Warrant may not be exercised as to fractional
shares of Common Stock. In the event that the exercise of this Warrant, in
full or in part, would result in the issuance of any fractional share of Common
Stock, then the number of Warrant Shares for which this Warrant shall have been
exercised shall be rounded up or down to the nearest whole number of Warrant
Shares.

4. Covenants Of the Company.

(a) The Company shall use its reasonable best efforts to
insure that a Registration Statement under the Act covering the issuance of the
Warrant Shares and the resale or other disposition thereof by the Warrant
Holder is effective as provided in the Registration Rights Agreement.

(b) The Company shall take all necessary action and
proceedings as may be required and permitted by applicable law, rule and
regulation, including, without limitation the notification of the National
Association of Securities Dealer, Inc., for the legal and valid issuance of
this Warrant and the Warrant Shares to the Warrant Holder under this Warrant.

(c) From the date hereof through the last date on which
this Warrant is exercisable, the Company shall take all steps reasonably
necessary and within its control to insure that the Common Stock remains listed
on the Exchange and shall not amend its Certificate of Incorporation or By-laws
so as to adversely affect in any material way any rights of the Warrant Holder
under this Warrant.

(d) The Company shall at all times reserve and keep
available, solely for issuance and delivery as Warrant Shares hereunder, such
shares of Common Stock as shall from time to time be issuable as Warrant
Shares.

(e) The Warrant Shares, when issued in accordance with
the terms hereof, will be duly authorized and, when issued in accordance with
the terms hereof, shall be validly issued, fully paid and non-assessable. The
Company has authorized and reserved for issuance to the Warrant Holder the
requisite number of shares of Common Stock to be issued pursuant to this
Warrant.

(f) With a view to making available to the Warrant Holder
the benefits of Rule 144 promulgated under the Act and any other rule or
regulation of the SEC that may at any time permit the Warrant Holder to sell
securities of the
<PAGE> 22
- 4 -

Company to the public without registration, the Company agrees to use its
reasonable best efforts to:

(i) make and keep public information available, as those
terms are understood and defined in Rule 144, at all times;

(ii) file with the SEC in a timely manner all reports and
other documents required of the Company under the Act and the Exchange
Act; and

(iii) furnish to any Warrant Holder forthwith upon request
a written statement by the Company that it has complied with the
reporting requirements of Rule 144 and of the Act and the Exchange
Act, a copy of the most recent annual or quarterly report of the
Company, and such other reports and documents so filed by the Company
as may be reasonably requested to permit any such Warrant Holder to
take advantage of any rule or regulation of the SEC permitting the
selling of any such securities without registration.

5. Adjustment of Exercise Price and Number of Shares. The number
of and kind of securities purchasable upon exercise of this Warrant and the
Purchase Price shall be subject to adjustment from time to time as follows:

(a) Subdivisions, Combinations and Other Issuances. If
the Company shall at any time after the date hereof but prior to the expiration
of this Warrant subdivide its outstanding securities as to which purchase
rights under this Warrant exist, by split-up, spin-off, or otherwise, or
combine its outstanding securities as to which purchase rights under this
Warrant exist, the number of Warrant Shares as to which this Warrant is
exercisable as of the date of such subdivision, split-up, spin-off or
combination shall forthwith be proportionately increased in the case of a
subdivision, or proportionately decreased in the case of a combination.
Appropriate adjustments shall also be made to the purchase price payable per
share, but the aggregate purchase price payable for the total number of Warrant
Shares purchasable under this Warrant as of such date shall remain the same.

(b) Stock Dividend. If at any time after the date hereof
the Company declares a dividend or other distribution on Common Stock payable
in Common Stock or other securities or rights convertible into or exchangeable
or exercisable for Common Stock ("Common Stock Equivalents") without payment of
any consideration by holders of Common Stock for the additional shares of
Common Stock or the Common Stock Equivalents (including the additional shares
of Common Stock issuable upon exercise or conversion thereof), then the number
of shares of Common Stock for which this Warrant may be exercised shall be
increased as of the record date (or the date of such dividend distribution if
no record date is set) for determining which holders of Common Stock shall be
entitled to receive such dividends, in proportion to the increase in the number
of outstanding shares (and
<PAGE> 23
- 5 -

shares of Common Stock issuable upon conversion of all such securities
convertible into Common Stock) of Common Stock as a result of such dividend,
and the Purchase Price shall be adjusted so that the aggregate amount payable
for the purchase of all the Warrant Shares issuable hereunder immediately after
the record date (or on the date of such distribution, if applicable) for such
dividend shall equal the aggregate amount so payable immediately before such
record date (or on the date of such distribution, if applicable).

(c) Other Distributions. If at any time after the date
hereof the Company distributes to holders of its Common Stock, other than as
part of its dissolution, liquidation or the winding up of its affairs, any
shares of its capital stock, any evidence of indebtedness or any of its assets
(other than cash, Common Stock or securities convertible into Common Stock),
then the Company shall decrease the per share Purchase Price of this Warrant by
an appropriate amount based upon the value distributed on each share of Common
Stock as determined in good faith by the Company's Board of Directors.

(d) Merger, etc. If at any time after the date hereof
there shall be a merger or consolidation of the Company with or into or a
transfer of all or substantially all of the assets of the Company to another
entity, then the Warrant Holder shall be entitled to receive upon such
transfer, merger or consolidation becoming effective, and upon payment of the
aggregate Purchase Price then in effect, the number of shares or other
securities or property of the Company or of the successor corporation resulting
from such merger or consolidation, which would have been received by the
Warrant Holder for the shares of stock subject to this Warrant had this Warrant
been exercised just prior to such transfer, merger or consolidation becoming
effective or to the applicable record date thereof, as the case may be.

(e) Reclassification, etc. If at any time after the date
hereof there shall be a reorganization or reclassification of the securities as
to which purchase rights under this Warrant exist into the same or a different
number of securities of any other class or classes, then the Warrant Holder
shall thereafter be entitled to receive upon exercise of this Warrant, during
the period specified herein and upon payment of the Purchase Price then in
effect, the number of shares or other securities or property resulting from
such reorganization or reclassification, which would have been received by the
Warrant Holder for the shares of stock subject to this Warrant had this Warrant
at such time been exercised.

(f) Purchase Price Adjustment. In the event that the
Company issues or sells any Common Stock or securities which are convertible
into or exchangeable for its Common Stock, or any warrants or other rights to
subscribe for or to purchase, or any options for the purchase of, its Common
Stock or any such convertible or exchangeable securities (other than shares or
options issued or which may be issued pursuant to the Company's employee or
director option plans or shares
<PAGE> 24
- 6 -

issued upon exercise of options, warrants or rights outstanding on the date of
the Agreement and listed in the Exchange Act Reports) at an effective purchase
price per share which is less than the Purchase Price then in effect or the
fair market value (as hereinabove defined), whichever is lower, of the Common
Stock on the trading day next preceding such issue or sale, then in each such
case, the Purchase Price in effect immediately prior to such issue or sale
shall be reduced effective concurrently with such issue or sale to an amount
determined by multiplying the Purchase Price then in effect by a fraction, (x)
the numerator of which shall be the sum of (1) the number of shares of Common
Stock outstanding immediately prior to such issue or sale, including, without
duplication, those deemed to have been issued under any provision of the
Debentures and the Warrants, plus (2) the number of shares of Common Stock
which the aggregate consideration received by the Company for such additional
shares would purchase at such fair market value or Purchase Price, as the case
may be, then in effect; and (y) the denominator of which shall be the number of
shares of Common Stock of the Company outstanding immediately after such issue
or sale including, without duplication, those deemed to have been issued under
any provision of the Debentures and Warrants. For purposes of the foregoing
fraction, Common Stock outstanding shall include, without limitation, any
Equity Offerings (as defined in the Debentures) then outstanding, whether or
not they are exercisable or convertible when such fraction is to be determined.

In the event of any such issuance for a consideration which is less
than such fair market value and also less than the Purchase Price then in
effect, then there shall be only one such adjustment by reason of such
issuance, such adjustment to be that which results in the greatest reduction of
the Purchase Price computed as aforesaid. The number of shares which may be
purchased hereunder shall be increased proportionately to any reduction in
Purchase Price pursuant to this paragraph 5(f), so that after such adjustments
the aggregate Purchase Price payable hereunder for the increased number of
shares shall be the same as the aggregate Purchase Price in effect just prior
to such adjustments.

6. No Impairment. The Company will not, by amendment of its
Certificate of Incorporation or through any reorganization, transfer of assets,
consolidation, merger, dissolution, issue or sale of securities or any other
voluntary action, avoid or seek to avoid the observance or performance of any
of the terms of this Warrant, but will at all times in good faith assist in the
carrying out of all such terms and in the taking of all such action as may be
necessary or appropriate in order to protect the rights of the Warrant Holder
against impairment. Without limiting the generality of the foregoing, the
Company (a) will not increase the par value of any Warrant Shares above the
amount payable therefor on such exercise, and (b) will take all such action as
may be reasonably necessary or appropriate in order that the Company may
validly and legally issue fully paid and nonassessable Warrant Shares on the
exercise of this Warrant.
<PAGE> 25
- 7 -

7. Notice of Adjustments; Notices. Whenever the Purchase Price
or number of Shares purchasable hereunder shall be adjusted pursuant to Section
5 hereof, the Company shall execute and deliver to the Warrant Holder a
certificate setting forth, in reasonable detail, the event requiring the
adjustment, the amount of the adjustment, the method by which such adjustment
was calculated and the Purchase Price and number of shares purchasable
hereunder after giving effect to such adjustment, and shall cause a copy of
such certificate to be mailed (by first class mail, postage prepaid) to the
Warrant Holder.

8. Rights As Stockholder. Prior to exercise of this Warrant, the
Warrant Holder shall not be entitled to any rights as a stockholder of the
Company with respect to the Warrant Shares, including (without limitation) the
right to vote such shares, receive dividends or other distributions thereon or
be notified of stockholder meetings. However, in the event of any taking by
the Company of a record of the holders of any class of securities for the
purpose of determining the holders thereof who are entitled to receive any
dividend (other than a cash dividend) or other distribution, any right to
subscribe for, purchase or otherwise acquire any shares of stock of any class
or any other securities or property, or to receive any other right, the Company
shall mail to each Warrant Holder, at least 10 days prior to the date specified
therein, a notice specifying the date on which any such record is to be taken
for the purpose of such dividend, distribution or right, and the amount and
character of such dividend, distribution or right.

9. Replacement of Warrant. On receipt of evidence reasonably
satisfactory to the Company of the loss, theft, destruction or mutilation of
the Warrant and, in the case of any such loss, theft or destruction of the
Warrant, on delivery of an indemnity agreement or security reasonably
satisfactory in form and amount to the Company or, in the case of any such
mutilation, on surrender and cancellation of such Warrant, the Company, upon
receipt by it of a form of Warrant reflecting the terms of the new Warrant, at
its expense will execute and deliver, in lieu thereof, a new Warrant of like
tenor.

10. Specific Enforcement; Consent to Jurisdiction.

(a) The Company and the Warrant Holder acknowledge
and agree that irreparable damage would occur in the event that any of the
provisions of this Warrant were not performed in accordance with their specific
terms or were otherwise breached. It is accordingly agreed that the parties
shall be entitled to an injunction or injunctions to prevent or cure breaches
of the provisions of this Warrant and to enforce specifically the terms and
provisions hereof, this being in addition to any other remedy to which either
of them may be entitled by law or equity.

(b) Each of the Company and the Warrant Holder (i)
hereby irrevocably submits to the exclusive jurisdiction of the United States
District Court
<PAGE> 26
- 8 -

for the Southern District of New York for the purposes of any suit, action or
proceeding arising out of or relating to this Warrant and (ii) hereby waives,
and agrees not to assert in any such suit, action or proceeding, any claim that
it is not personally subject to the jurisdiction of such court, that the suit,
action or proceeding is brought in an inconvenient forum or that the venue of
the suit, action or proceeding is improper. Each of the Company and the
Warrant Holder consents to process being served in any such suit, action or
proceeding by mailing a copy thereof to such party at the address in effect for
notices to it under this Warrant and agrees that such service shall constitute
good and sufficient service of process and notice thereof. Nothing in this
paragraph shall affect or limit any right to serve process in any other manner
permitted by law.

11. Entire Agreement; Amendments. This Warrant, the Exhibits
hereto and the provisions contained in the Agreement, the Registration Rights
Agreement or the Debentures and incorporated into this Warrant and the Warrant
Shares contain the entire understanding of the parties with respect to the
matters covered hereby and thereby and, except as specifically set forth herein
and therein, neither the Company nor the Warrant Holder makes any
representation, warranty, covenant or undertaking with respect to such matters.
No provision of this Agreement may be waived or amended other than by a written
instrument signed by the party against whom enforcement of any such amendment
or waiver is sought.

12. Restricted Securities. Sections 4.5, 5.1, 5.2 and 5.3 of the
Agreement are incorporated herein by reference and hereby made a part hereof.

13. Notices. Any notice or other communication required or
permitted to be given hereunder shall be in writing and shall be effective (a)
upon hand delivery or receipt by telex (with correct answer back received),
telecopy or facsimile at the address or number designated below (if delivered
on a business day during normal business hours where such notice is to be
received), or the first business day following such delivery (if delivered
other than on a business day during normal business hours where such notice is
to be received), or (b) on the second business day following the date of
mailing by express courier service, fully prepaid, addressed to such address,
or upon actual receipt of such mailing, whichever shall first occur. The
addresses for such communications shall be:

to the Company:

Oncor, Inc.
209 Perry Parkway
Gaithersburg, Maryland 20877
Attn: President
Fax: (301) 330-3940
<PAGE> 27
- 9 -

with copies to:

Brobeck, Phleger & Harrison LLP
1301 Avenue of the Americas, 30th Floor
New York, NY 10019
Attn: Alexander D. Lynch, Esq.
Fax: (212) 586-7878

to the Warrant Holder:

with copies to:

Promethean Investment Group, L.L.C.
40 West 57th Street
Suite 1520
New York, NY 10019
Attn: Thomas Lumsden
Fax: (212) 698-0505

Either party hereto may from time to time change its address for notices under
this Section 13 by giving at least 10 days prior written notice of such changed
address to the other party hereto.

14. Miscellaneous. This Warrant and any term hereof may be
changed, waived, discharged or terminated only by an instrument in writing
signed by the party against which enforcement of such change, waiver, discharge
or termination is sought. This Warrant shall be construed and enforced in
accordance with and governed by the laws of the State of New York. The
headings in this Warrant are for purposes of reference only, and shall not
limit or otherwise affect any of the terms hereof. The invalidity or
unenforceability of any provision hereof shall in no way affect the validity or
enforceability of any other provision.

15. Expiration. The right to exercise this Warrant shall expire
sixty (60) months after the date hereof.
<PAGE> 28
- 10 -

[Signatures on next page.]
<PAGE> 29
- 11 -

Dated: December 30, 1996 ONCOR, INC.

By:
-----------------------------------
Title:
-------------------------------

[CORPORATE SEAL]

Attest:

By:
-----------------------
Its:

NAME OF INVESTOR:

-----------------------
By its: Director and
Authorized Signatory

By:
-----------------------------------
Name:
-----------------------------
Title:
--------------------------------

<PAGE> 30
- 12 -

FORM OF WARRANT EXERCISE
(TO BE SIGNED ONLY ON EXERCISE OF WARRANT)

TO
-------------------------

The undersigned, the holder of the within Warrant, hereby irrevocably
elects to exercise this Warrant for, and to purchase thereunder, _________
shares of Common Stock of Oncor, Inc., a Maryland corporation (the "Company"),
and herewith makes payment of $__________ therefor, and requests that the
certificates for such shares be issued in the name of, and delivered to
_________________, whose address is __________________.

Dated:
----------------------------------

(Signature must conform to name of
holder as specified on the face of
the Warrant)

----------------------------------
(Address)

Tax Identification Number:
----------

<PAGE> 31
FORM OF ASSIGNMENT
(TO BE SIGNED ONLY ON TRANSFER OF WARRANT)

For value received, the undersigned hereby sells, assigns, and transfers unto
_________________ the right represented by the within Warrant to purchase
_____________ shares of Common Stock of Oncor, Inc., a Maryland corporation, to
which the within Warrant relates, and appoints _________________ Attorney to
transfer such right on the books of Oncor, Inc., with full power of
substitution the premises.

Dated:
----------------------------------

(Signature must conform to name of
holder as specified on the face of
the Warrant)

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

(Address)
Signed in the presence of:

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

<PAGE> 32

EXHIBIT A

PIK STATEMENT

Date:
-----------------------------------

To:
------------------------------------- ("Holder")

Re: 6% Convertible Debenture Due December 30, 2001 ("Debenture") of
Oncor, Inc. (the "Company") No. ________, in the face amount of U.S.
$ .

In lieu of paying interest on the above-referenced Debenture in coin or
currency, the Company hereby elects to pay interest on the Debenture, for the
Interest Payment Date indicated below, by having the amount of such interest
added to the Outstanding Principal Amount due under the Debenture. The Company
hereby certifies to the Holder, its successors and assigns that the Outstanding
Principal Amount due under the Debenture after delivery of this PIK Statement
equals the amount indicated below. Capitalized terms used in this PIK Statement
and not otherwise defined shall have the meaning ascribed thereto in the
Debenture.

Interest Payment Date:
----------------------------

Outstanding Principal Amount prior to issuance of U.S. $
this PIK Statement:
PIK Interest: U.S. $
Outstanding Principal Amount after issuance of U.S. $
this PIK Statement:

IN WITNESS WHEREOF, this PIK Statement has been duly executed and delivered
on the date first written above.

ONCOR, INC.

By:
------------------------------------
Name:
Title:
<PAGE> 33

EXHIBIT B

CONVERSION NOTICE
FOR 6% CONVERTIBLE DEBENTURES
DUE DECEMBER 30, 2001

The undersigned, as Holder of the 6% Convertible Debenture Due December 30,
2001 or Oncor, Inc., No. , in the Outstanding Principal Amount of U.S.
$ (the "Debenture"), hereby irrevocably elects to convert U.S.
$ of the outstanding principal amount of the Debenture and U.S.
$ of interest accrued but unpaid under the Debenture into shares of
Common Stock, par value $.01 per share (the "Common Stock"), of Oncor, Inc.
according to the conditions of the Debenture, as of the date written below.
Capitalized terms used in this Conversion Notice and not otherwise defined shall
have the meaning ascribed thereto in the Debenture.

Accompanying this Conversion Notice is a Computation Schedule setting forth
the determination by the undersigned of the number of shares of Common Stock
issuable pursuant to this Conversion Notice.

[In addition, pursuant to Paragraph 5(d) of the Debenture, the undersigned
hereby elects to purchase Additional Shares. The purchase price per
share for the Additional Shares, calculated in accordance with Paragraph 5(d),
shall be the Conversion Date Market Price set forth on the attachment hereto, or
$ . A wire transfer in the amount of the purchase price for the
Additional Shares shall be initiated to the account of Oncor, Inc. last
specified in writing by Oncor, Inc. to the undersigned.(1)]

The undersigned hereby requests that share certificates for the Common
Stock to be issued to the undersigned pursuant to this Conversion Notice [and
the Additional Shares] be issued in the name of, and delivered to, the
undersigned or its designee as indicated below. If shares are to be issued in
the name of a person other than the undersigned, the undersigned will pay all
transfer taxes payable with respect thereto. No

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

1Right to purchase may only be exercised if the Conversion Date Market
Price is equal to or greater than $4.00 (as adjusted), and the Holder may only
purchase Additional Shares in an amount up to the number of shares of Common
Stock issuable upon conversion of the Debenture.
<PAGE> 34

-2-

fee will be charged to the Holder for any conversion [or the purchase of
Additional Shares], except for transfer taxes, if any.

Holder:

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

By:

------------------------------------
Name:
Title:

Address of Holder:

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

Issue Common Stock [and Additional
Shares] to:

-------------------------------
at:

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

--------------------------------------
Holder Conversion Date
<PAGE> 35
COMPUTATION SCHEDULE

I. Calculation of Shares Issuable upon Conversion

(A) PRINCIPAL AMOUNT PLUS INTEREST:

(i) principal amount of Debenture submitted for conversion, plus $
---------
(ii) accrued but unpaid interest on principal amount of
Debenture submitted for conversion $
---------
Total: (A) $
---------

(B) CONVERSION DATE MARKET PRICE: THE LESSER OF

(i) (a) average market Price for Shares for Common Stock for
the five trading days preceding the Holder Conversion
Date, multiplied by $
---------
(b) the Applicable Percentage $
---------
x %
---------

(i) $
---------
(ii) the Maximum Conversion Price (ii) $
---------
CONVERSION DATE MARKET PRICE
(THE LESSER OF (i) AND (ii)): (B) $
---------

NUMBER OF SHARES OF COMMON STOCK ISSUABLE
UPON CONVERSION ((A)/(B)):
---------

II. Number of Additional Shares to be Purchased hereunder

---------
III. Total Purchase Price for Additional Shares
---------

<PAGE> 1

EXHIBIT 4.4

Right to Purchase __________ Shares of Common Stock of Oncor, Inc.

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

Common Stock Purchase Warrant

Oncor, Inc., a Maryland corporation having an address at 209 Perry
Parkway, Gaithersburg, Maryland 20877, (the "Company"), hereby certifies that
for Ten United States Dollars ($10.00) and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged,
___________________, having an address at __________________________________
("Purchaser") or any other Warrant Holder is entitled, on the terms and
conditions set forth below, to purchase from the Company at any time after the
date hereof and ending sixty (60) months after the date hereof _______________
(______) shares of fully paid and nonassessable shares of Common Stock, $.01
par value, of the Company (the "Common Stock"), at the Purchase Price
(hereinafter defined), as the same may be adjusted pursuant to Section 5
herein.

1. Definitions.

(a) the term "Warrant" shall mean this Common Stock Purchase
Warrant, sometimes referred to in the Agreement as the Second Warrant.

(c) the term "Warrant Shares" shall mean the shares of Common
Stock or other securities issuable upon exercise of this Warrant.

(d) the term "Purchase Price" shall mean __________ Dollars
and __________ Cents United States Dollars ($_____) per share of Common
Stock[135% of the average Market Price for Shares of Common Stock for the five
trading days immediately preceding the Holder Conversion Date].

(e) the term "Act" shall mean the Securities Act of 1933, as
amended.

(f) the term "Exchange Act" shall mean the Securities and
Exchange Act of 1934, as amended.

(g) the term "SEC" or "Commission" shall mean the Securities
and Exchange Commission or any successor agency.

(h) the term "Rule 144" shall mean Rule 144 promulgated under
the Act, as amended, and any successor rules promulgated under the Act.

(i) other terms used herein which are defined in the
Subscription Agreement (the "Agreement") between the Company and the Purchaser
shall have the same meanings herein as therein.

2. Exercise of Warrant.

3. Delivery of Stock Certificates.

the name of and delivered to the Warrant Holder, or as the Warrant Holder (upon
payment by the Warrant Holder of any applicable transfer taxes) may lawfully
direct, a certificate or certificates for the number of fully paid and
non-assessable shares of Common Stock to which the Warrant Holder shall be
entitled on such exercise, together with any other stock or other securities or
property (including cash, where applicable) to which the Warrant Holder is
entitled upon such exercise.

4. Covenants Of the Company.

(f) With a view to making available to the Warrant Holder
the benefits of Rule 144 promulgated under the Act and any other rule or
regulation of
<PAGE> 4
- 4 -

the SEC that may at any time permit the Warrant Holder to sell securities of
the Company to the public without registration, the Company agrees to use its
reasonable best efforts to:

(i) make and keep public information available, as those
terms are understood and defined in Rule 144, at all times;

(ii) file with the SEC in a timely manner all reports and
other documents required of the Company under the Act and the Exchange
Act; and

dividends, in proportion to the increase in the number of outstanding shares
(and shares of Common Stock issuable upon conversion of all such securities
convertible into Common Stock) of Common Stock as a result of such dividend,
and the Purchase Price shall be adjusted so that the aggregate amount payable
for the purchase of all the Warrant Shares issuable hereunder immediately after
the record date (or on the date of such distribution, if applicable) for such
dividend shall equal the aggregate amount so payable immediately before such
record date (or on the date of such distribution, if applicable).

may be issued pursuant to the Company's employee or director option plans or
shares issued upon exercise of options, warrants or rights outstanding on the
date of the Agreement and listed in the Exchange Act Reports) at an effective
purchase price per share which is less than the Purchase Price then in effect
or the fair market value (as hereinabove defined), whichever is lower, of the
Common Stock on the trading day next preceding such issue or sale, then in each
such case, the Purchase Price in effect immediately prior to such issue or sale
shall be reduced effective concurrently with such issue or sale to an amount
determined by multiplying the Purchase Price then in effect by a fraction, (x)
the numerator of which shall be the sum of (1) the number of shares of Common
Stock outstanding immediately prior to such issue or sale, including, without
duplication, those deemed to have been issued under any provision of the
Debentures and the Warrants, plus (2) the number of shares of Common Stock
which the aggregate consideration received by the Company for such additional
shares would purchase at such fair market value or Purchase Price, as the case
may be, then in effect; and (y) the denominator of which shall be the number of
shares of Common Stock of the Company outstanding immediately after such issue
or sale including, without duplication, those deemed to have been issued under
any provision of the Debentures and Warrants. For purposes of the foregoing
fraction, Common Stock outstanding shall include, without limitation, any
Equity Offerings (as defined in the Debentures) then outstanding, whether or
not they are exercisable or convertible when such fraction is to be determined.

10. Specific Enforcement; Consent to Jurisdiction.

(b) Each of the Company and the Warrant Holder (i)
hereby irrevocably submits to the exclusive jurisdiction of the United States
District Court for the Southern District of New York for the purposes of any
suit, action or proceeding arising out of or relating to this Warrant and (ii)
hereby waives, and agrees not to assert in any such suit, action or proceeding,
any claim that it is not personally subject to the jurisdiction of such court,
that the suit, action or proceeding is brought in an inconvenient forum or that
the venue of the suit, action or proceeding is improper. Each of the Company
and the Warrant Holder consents to process being served in any such suit,
action or proceeding by mailing a copy thereof to such party at the address in
effect for notices to it under this Warrant and agrees that such service shall
constitute good and sufficient service of process and notice thereof. Nothing
in this paragraph shall affect or limit any right to serve process in any other
manner permitted by law.

12. Restricted Securities. Sections 4.5, 5.1, 5.2 and 5.3 of the
Agreement are incorporated herein by reference and hereby made a part hereof.

to the Company:

Oncor, Inc.
209 Perry Parkway
Gaithersburg, Maryland 20877
Attn: President
<PAGE> 9
- 9 -

Fax: (301) 330-3940

with copies to:

Brobeck, Phleger & Harrison LLP
1301 Avenue of the Americas, 30th Floor
New York, NY 10019
Attn: Alexander D. Lynch, Esq.
Fax: (212) 586-7878

to the Warrant Holder:

with copies to:

Promethean Investment Group, L.L.C.
40 West 57th Street
Suite 1520
New York, NY 10019
Attn: Thomas Lumsden
Fax: (212) 698-0505

Either party hereto may from time to time change its address for notices under
this Section 13 by giving at least 10 days prior written notice of such changed
address to the other party hereto.

15. Expiration. The right to exercise this Warrant shall expire
sixty (60) months after the date hereof.

[Signatures on next page.]
<PAGE> 11
- 11 -

Dated: ONCOR, INC.
------ --, ----

By:
----------------------------------
Title:
------------------------------

[CORPORATE SEAL]

Attest:

By:
-----------------------
Its:

NAME OF INVESTOR:

-----------------------
By its: Director and
Authorized Signatory

By:
----------------------------------
Name:
-----------------------------
Title:
-------------------------------

<PAGE> 12

FORM OF WARRANT EXERCISE
(TO BE SIGNED ONLY ON EXERCISE OF WARRANT)

TO
-------------------------

Dated:
----------------------------------

(Signature must conform to name of
holder as specified on the face of
the Warrant)

----------------------------------
(Address)

Tax Identification Number:
-------------
<PAGE> 13
FORM OF ASSIGNMENT
(TO BE SIGNED ONLY ON TRANSFER OF WARRANT)

Dated:
----------------------------------

(Signature must conform to name of
holder as specified on the face of
the Warrant)

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

(Address)
Signed in the presence of:

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

<PAGE> 1
EXHIBIT 5

February 28, 1997

Oncor, Inc.
209 Perry Parkway
Gaithersburg, Maryland 20877

Re: Registration Statement on Form S-3

Gentlemen and Ladies:

We have examined the Registration Statement on Form S-3 to be
filed by you with the Securities and Exchange Commission (the "Commission") in
connection with the registration under the Securities Act of 1933, as amended,
of the sale by certain stockholders of 4,907,645 shares of your Common Stock
(the "Shares"). The Shares include 4,903,170 shares issuable by the Company
(i) upon the conversion of 6% Convertible Debentures due December 30, 2001 (the
"Debentures"), (ii) upon the exercise of certain warrants (the "Warrants") and
(iii) upon the exercise of certain options to purchase additional shares of
Common Stock (the "Options"). The shares issuable upon the conversion or
exercise of the Debentures, Warrants or Options are being offered by certain
stockholders of the Company. The Shares also include 4,475 shares issued to an
individual stockholder (the "Stockholder Shares"). As your counsel, we have
examined the proceedings taken and are familiar with the proceedings proposed
to be taken by you in connection with the transactions described in the
Registration Statement.

We have examined such records and documents and have made such
examination of laws as we considered necessary to form a basis for the opinion
set forth herein. In our examination, we have assumed the genuineness of all
signatures, the authenticity of all documents submitted to us as originals, and
the conformity with the originals of all documents submitted to us as copies
thereof.

Based upon and subject to the foregoing, it is our opinion
that:

(1) The Shares issuable upon the exercise of the
Warrants, when issued and sold in accordance with the terms of the Warrants and
in the manner described in the Registration Statement, the Shares issuable upon
the conversion of the Debentures, when
<PAGE> 2
Oncor, Inc. February 28, 1997
Page 2

issued and sold in accordance with the terms of the Debentures and in the
manner described in the Registration Statement and the Shares issuable upon the
exercise of the Options, when issued and sold in accordance with the terms of
the Options and in the manner described in the Registration Statement, will be
validly issued, fully paid and nonassessable.

(2) The Stockholder Shares when issued were, and when
sold in the manner described in the Registration Statement will be, validly
issued, fully paid and non-assessable.

We hereby consent to the use of our name in the Registration
Statement under the caption "Legal Matters" in the related Prospectus and
consent to the filing of this opinion as an exhibit thereto.

Very truly yours,

/s/ Brobeck, Phleger & Harrison LLP
BROBECK, PHLEGER & HARRISON LLP

<PAGE> 1

EXHIBIT 10.1

SUBSCRIPTION AGREEMENT

This Subscription Agreement (this "Agreement"), dated as of December
30, 1996, has been executed by the undersigned (the "Subscriber") in connection
with (a) the sale of 6% Convertible Debentures due December 30, 2001 (the
"Debentures") of Oncor, Inc., a Maryland corporation, having an address at 209
Perry Parkway, Gaithersburg, Maryland 20877 (the "Company"), convertible into
shares of Common Stock, par value $.01 per share (the "Common Stock"), of the
Company, and (b) the issuance by the Company of its warrants to purchase up to
250,000 shares of Common Stock (the "First Warrants"). The Company is offering
an aggregate amount of up to $10,000,000 of Debentures, together with the First
Warrants, at an aggregate price of up to $10,000,000 (the "Offering"). In
addition, the Debentures provide that, under certain circumstances, certain
holders may be entitled to receive Second Warrants (as defined in the
Debentures). The form of the Debentures to be purchased by the Subscriber
hereunder, including the terms on which such Debentures may be converted into
Common Stock, is attached hereto as Exhibit A. The form of the First Warrants,
including the terms upon which the First Warrants may be exercised, is attached
hereto as Exhibit B. The solicitation of this Agreement and, if accepted by
the Company, the offer and sale of the Debentures and the Warrants, are being
made in reliance upon the provisions of Regulation D ("Regulation D")
promulgated by the Securities and Exchange Commission ("SEC") under the
Securities Act of 1933, as amended (the "Securities Act"), or under the
exemption from registration set forth in Section 4(2) of the Securities Act.
The First Warrants and the Second Warrants (as defined in the Debentures) are
sometimes collectively referred to as the "Warrants." The Additional Shares
(as defined in the Debentures) and the Common Stock issuable upon the
conversion or exercise of the Debentures and Warrants, respectively, are
sometimes collectively referred to as the "Shares." The Debentures, the
Warrants and the Shares are sometimes collectively referred to in this
Agreement as the "Securities."

The Subscriber wishes to subscribe for, and the Company wishes to
issue, the aggregate principal amount of Debentures and the number of First
Warrants at the aggregate purchase price set forth in Section 14 and in
accordance with the other terms and conditions of this Agreement. In
consideration of the mutual promises, representations, warranties and
conditions set forth herein, and intending to be legally bounded hereby, the
Company and the Subscriber agree as follows:

1. PURCHASE AND SALE OF SECURITIES; CLOSING CONDITIONS.

1.1. Purchase and Sale of Securities.
<PAGE> 2
- 2 -

(a) Purchase of Debentures and First Warrants. The
Company shall issue and sell to the Subscriber and the Subscriber shall
purchase from the Company such number of Debentures and First Warrants as is
set forth in Section 14 hereof for an aggregate purchase price equal to
____________________ Dollars (U.S. $_______) ("Purchase Price"). The issuance,
sale and purchase of the Debentures and First Warrants shall take place in one
closing (the "Closing").

(b) Form of Payment. On the Closing Date (as defined
below), (i) the Subscriber shall pay the Purchase Price for the Securities to
be issued and sold at the Closing by wire transfer to the Company, in
accordance with the Company's written wiring instructions, against delivery of
duly executed Debentures and First Warrants which the Subscriber is purchasing,
and (ii) the Company shall deliver to Subscriber such Debentures and First
Warrants against delivery of such Purchase Price.

(c) Closing Date. Subject to the satisfaction (or
waiver) of the conditions thereto set forth in Section 1.2 and Section 1.3
below, the date and time of the issuance and sale of the Debentures and First
Warrants pursuant to this Agreement shall be 12:00 noon Eastern Standard Time
on December 30, 1996 (the "Closing Date") (subject to a two (2) business day
grace period at either party's option), or, in each case, at such other
mutually agreed upon time. The Closing shall occur on the Closing Date at such
place and time as the parties shall determine.

1.2. Conditions Precedent to the Obligation of the Company to Issue
and Sell the Debentures and First Warrants. The obligation hereunder of the
Company to issue and/or sell the Debentures and First Warrants to the
Subscriber at the Closing is subject to the satisfaction, at or before the
Closing Date, of each of the conditions set forth below. These conditions are
for the Company's sole benefit and may be waived by the Company at any time in
its sole discretion.

(a) Payment of Purchase Price. The Subscriber shall have
delivered to the Company the Purchase Price payable by the Subscriber at the
Closing.

(b) Accuracy of the Subscriber's Representation and
Warranties. The representations and warranties of the Subscriber shall be true
and correct as of the date when made and as of the Closing Date as though made
at such time.

(c) Performance by the Subscriber. The Subscriber shall
have performed, satisfied and complied in all respects with all covenants,
agreements and conditions required by this Agreement to be performed, satisfied
or complied with by the Subscriber at or prior to the Closing.
<PAGE> 3
- 3 -

(d) No Injunction. No statute, rule, regulation,
executive order, decree, ruling or injunction shall have been enacted, entered,
promulgated or endorsed by any court or governmental authority of competent
jurisdiction which prohibits or adversely affects any of the transactions
contemplated by this Agreement, and no proceeding shall have been commenced
which may have the effect of prohibiting or adversely affecting any of the
transactions contemplated by this Agreement.

1.3. Conditions Precedent to the Obligation of the Subscriber to
Acquire the Debentures and First Warrants. The obligation of Subscriber
hereunder to acquire and pay for the Debentures and First Warrants at the
Closing is subject to the satisfaction, at or before the Closing Date, of each
of the following conditions. Each of these conditions is for Subscriber's sole
benefit and may be waived by Subscriber at any time in its sole discretion.

(a) Accuracy of the Company's Representations and
Warranties. The representations and warranties of the Company shall
be true and correct as of the date when made and as of the Closing
Date as though made at each such time.

(b) Performance by the Company. The Company shall have
performed, satisfied and complied in all respects with all covenants,
agreements and conditions required by this Agreement to be performed,
satisfied or complied with by the Company at or prior to the Closing.

(c) No Injunction. No statute, rule, regulation,
executive order, decree, ruling or injunction shall have been enacted,
entered, promulgated or endorsed by any court or governmental
authority of competent jurisdiction which prohibits or adversely
effects any of the transactions contemplated by this Agreement, and no
proceeding shall have been commenced which may have the effect of
prohibiting or adversely affecting any of the transactions
contemplated by this Agreement.

(d) Adverse Changes. Since September 30, 1996, except as
set forth on Schedule 1.3, no event has occurred which has had or is
likely to have a material adverse effect on the financial condition,
earnings, operations or business of the Company.

(e) No Suspension of Trading In or Delisting of Common
Stock. As of the Closing Date, the trading of the Common Stock shall
not have been suspended by the SEC, the American Stock Exchange (the
"Exchange") or the National Association of Securities Dealers, Inc.
(the "NASD"), and the Common Stock shall not have been delisted from
the Exchange.
<PAGE> 4
- 4 -

(f) The Legal Opinion. The Company shall have delivered
to the Subscriber the opinion of Brobeck, Phleger & Harrison LLP,
independent counsel to the Company, dated as of the Closing Date and
in form and substance reasonably satisfactory to the Subscriber.

(g) Officer's Certificate. The Company shall have
delivered to the Subscriber a certificate in form and substance
reasonably satisfactory to the Subscriber, executed by an executive
officer of the Company as of the Closing Date, to the effect that all
the conditions to the Closing set forth in this Section 1.3 shall have
been satisfied.

(h) Registration Rights Agreement. The Company and the
Subscriber shall have entered into the Registration Rights Agreement,
in the form of Exhibit C annexed hereto (the "Registration Rights
Agreement").

(i) Transfer Agent Irrevocable Instruction. The Company
shall have delivered to the transfer agent for its Common Stock the
Transfer Agent Irrevocable Instruction, in the form of Exhibit D
annexed hereto.

(j) Pledge Agreement. The Company and the Subscriber
shall have entered into the Pledge Agreement, in the form of Exhibit E
annexed hereto (the "Pledge Agreement").

2. REPRESENTATIONS AND WARRANTIES OF SUBSCRIBER.

The Subscriber represents and warrants to the Company that:

2.1. No Government Recommendation or Approval. The Subscriber
understands that no United States federal or state agency or similar agency of
any other country has passed upon or made any recommendation or endorsement of
the Company or the offering of the Securities.

2.2. Intent. The Subscriber is purchasing the Securities for its
own account and not with a view towards distribution and the Subscriber has no
present arrangement (whether or not legally binding) at any time to sell the
Securities to or through any person or entity; provided, however, that by
making the representations herein, the Subscriber does not agree to hold the
Securities for any minimum or other specific term and reserves the right to
dispose of the Securities at any time in accordance with federal and state
securities laws applicable to such disposition. The Subscriber understands
that the Securities must be held indefinitely unless such Securities are
subsequently registered under the Securities Act or an exemption from
registration is available. The Subscriber has been advised or is aware of the
provisions of Rule 144.
<PAGE> 5
- 5 -

2.3. Sophisticated Investor. The Subscriber is a sophisticated
investor (as described in Rule 506(b)(2)(ii) of Regulation D promulgated under
the Securities Act ("Regulation D")) and an accredited investor (as defined in
Rule 501 of Regulation D), and Subscriber has such experience in business and
financial matters that it is capable of evaluating the merits and risks of an
investment in the Securities. The Subscriber acknowledges that the Securities
are speculative and involve a high degree of risk.

2.4. Independent Investigation. The Subscriber, in making its
decision to purchase the Securities subscribed for hereunder, has relied upon
an independent investigation made by it and/or its representatives and has not
relied on any information or representations made by third parties or on any
oral or written representations or assurances from the Company or any
representative or agent of the Company, other than as set forth in this
Agreement, in the public filings of the Company and in the documents described
below. Prior to the date hereof, the Subscriber has been furnished with and
has reviewed the Company's latest proxy statement and Annual Report on Form
10-K sent to the Company's shareholders and all documents filed by the Company
with the SEC since December 31, 1995 pursuant to sections 13(a), 13(c), 14 or
15(d) of the Securities Exchange Act of 1934, as amended (the "Exchange Act")
(excluding preliminary proxy statement filings) (such documents are
collectively referred to in this Agreement as the "Exchange Act Reports"). The
Subscriber has had a reasonable opportunity to ask questions of and receive
answers from the Company concerning the Company and the Offering. The
Subscriber acknowledges that the price and terms of the Securities offered
hereby has been determined by negotiation based, in part, on the market price
for the Common Stock, and does not necessarily bear any relationship to the
assets, book value or potential performance of the Company or any other
recognized criteria of value.

2.5. Authority. This Agreement has been duly authorized and
validly executed and delivered by the Subscriber and is a valid and binding
agreement of the Subscriber enforceable against the Subscriber in accordance
with its terms, subject to general principles of equity and to bankruptcy or
other laws affecting the enforcement of creditors' rights generally.

2.6. No Legal Advice From Company. The Subscriber acknowledges
that it has had the opportunity to review this Agreement and the transactions
contemplated by this Agreement with his or its own legal counsel and tax
advisors. Except for any statements or representations of the Company made in
this Agreement and in the Exchange Act Reports, the Subscriber is relying
solely on such counsel and advisors and not on any statements or
representations of the Company or any of its representative or agents for
legal, tax or investment advice with respect to this investment, the
transactions contemplated by this Agreement or the securities laws of any
jurisdiction.
<PAGE> 6
- 6 -

2.7. No Brokers. The Subscriber has taken no action which would
give rise to any claim by any person for brokerage commissions, finder's fees
or similar payments by the Company relating to this Agreement or the
transactions contemplated hereby, except for dealings with Promethean
Investment Group, L.L.C., whose fees will be paid for by the Subscriber.

2.8 Not an Affiliate. The Subscriber is not an officer, director
or "affiliate" (as that term is defined in Rule 405 of the Securities Act) of
the Company.

2.9. Reliance on Representations and Warranties. The Subscriber
understands that the Securities are being offered and sold to it in reliance on
specific provisions of United States federal and state securities laws and that
the Company is relying upon the truth and accuracy of the representations,
warranties, agreements, acknowledgments and understandings of the Subscriber
set forth in this Agreement in order to determine the applicability of such
provisions.
<PAGE> 7
- 7 -

3. REPRESENTATIONS AND WARRANTIES OF THE COMPANY.

The Company represents and warrants to the Subscriber that:

3.1. Company Status. The Company has registered its Common Stock
pursuant to Section 12(b) or 12(g) of the Exchange Act, is in full compliance
with all reporting requirements of the Exchange Act, and the Company has
maintained all requirements for the continued listing of its Common Stock, and
such Common Stock is currently listed on the Exchange.

3.2. Current Public Information. The Exchange Act Reports listed
on Schedule 1 hereto are the only filings made by the Company since December
31, 1995 pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act.

3.3. No Directed Selling Efforts or General Solicitation in Regard
to this Transaction. Neither the Company nor any of its affiliates nor any
distributor or any person acting on its or their behalf has conducted any
"directed selling efforts" with respect to the Debentures or the Warrants nor
has the Company conducted any general solicitation (as that term is used in
Regulation D) with respect to any of the Securities, nor has any such person
made any offers or sales of any security or solicited any offers to buy any
security, under circumstances that would require registration of the Securities
under the Act.

3.4. Capitalization; Valid Issuance of Debentures and Capital
Stock. The Company has an authorized capitalization consisting of 50,000,000
shares of Common Stock, par value $.01 per share, and 1,000,000 shares of
Preferred Stock, par value $0.01 per share, convertible notes and unit options
outstanding that are convertible into or exercisable for up to an aggregate of
169,136 shares of Common Stock, debentures and warrants outstanding pursuant to
the Subscription Agreements dated August 27, 1996, and stock options granted to
employees as described in the Exchange Act Reports. The Company has 23,897,464
shares of Common Stock issued, of which 23,818,055 of such shares are
outstanding. None of such Preferred Stock has been issued or is outstanding.
All of the issued shares of Common Stock of the Company have been duly and
validly authorized and issued and are fully paid and non-assessable; upon
issuance of the Securities, the Securities will be duly and validly issued,
fully paid and non-assessable; the shares of Common Stock issuable upon
conversion of the Debentures (including Additional Shares) and exercise of the
Warrants, when issued and delivered in accordance with the terms of the
Debentures and the Warrants, respectively, will be duly and validly issued,
fully paid and non-assessable; and the holders of outstanding capital stock of
the Company are not and shall not be entitled to preemptive or other rights
afforded by the Company to subscribe for the capital stock or other securities
of the Company as a result of the
<PAGE> 8
- 8 -

sale of the Securities or the issuance of Common Stock upon the conversion or
exercise thereof.

3.5. Organization and Qualification. The Company is a corporation
duly incorporated and existing in good standing under the laws of the State of
Maryland and has the requisite corporate power to own its properties and to
carry on its business as now being conducted. The Company does not have any
subsidiaries, except for those listed on Schedule 2 annexed hereto and hereby
made a part hereof. The Company and each such subsidiary, if any, is duly
qualified as a foreign corporation to do business and is in good standing in
every jurisdiction in which the nature of the business conducted or property
owned by it makes such qualification necessary other than those in which the
failure so to qualify would not have a Material Adverse Effect. "Material
Adverse Effect" means any effect on the business, operations, properties,
prospects, or financial condition of the entity with respect to which such term
is used and which is material and adverse to such entity or to other entities
controlling or controlled by such entity, and/or any condition or situation
which would prohibit or otherwise interfere with the ability of the entity with
respect to which said term is used to enter into and perform its obligations
under this Agreement.

3.6. Authorization; Enforcement. (i) The Company has the requisite
corporate power and authority to enter into and perform this Agreement and to
issue the Securities in accordance with the terms hereof and thereof; (ii) the
execution, delivery and performance of this Agreement, the Debentures and the
Warrants by the Company and the consummation by it of the transactions
contemplated hereby and thereby, including without limitation the issuance of
Common Stock upon the conversion or exercise thereof, have been duly authorized
by all necessary corporate action, and no further consent or authorization of
the Company or its Board of Directors or stockholders is required; (iii) this
Agreement has been duly executed and delivered by the Company, and (iv) this
Agreement and the Debentures and Warrants constitute, and upon issuance and
delivery thereof the Debentures and Warrants shall be, valid and binding
obligations of the Company enforceable against the Company in accordance with
their terms, except as such enforceability may be limited by applicable
bankruptcy, insolvency, or similar laws relating to, or affecting generally the
enforcement of, creditors' rights and remedies or by other equitable principles
of general application.

3.7. Corporate Documents. The Company has furnished or made
available to the Subscriber true and correct copies of the Company's
Certificate of Incorporation as amended and in effect on the date hereof (the
"Certificate"), and the Company's By-Laws as amended and in effect on the date
hereof (the "By-Laws").

3.8. No Conflicts. The execution, delivery and performance by the
Company of this Agreement, the Registration Rights Agreement and the Debentures
<PAGE> 9
- 9 -

and Warrants and the consummation by the Company of the transactions
contemplated hereby and thereby, including without limitation the issuance of
Common Stock upon the conversion or exercise thereof, do not and will not (i)
result in a violation of the Certificate or By-Laws or (ii) conflict with or
constitute a default (or an event which with notice or lapse of time or both
would become a default) under, or give to others any rights of termination,
amendment, acceleration or cancellation of, any material agreement, indenture
or instrument to which the Company or any of its subsidiaries is a party, or
result in a violation of any federal, state, local or foreign law, rule,
regulation, order, judgment or decree (including federal and state securities
laws and regulations) applicable to the Company or any of its subsidiaries or
by which any property or asset of the Company or any of its subsidiaries is
bound or affected (except for such conflicts, defaults, terminations,
amendments, accelerations, cancellations and violations as would not,
individually or in the aggregate, have a Material Adverse Effect); provided,
that, for purposes of such representation as to federal, state, local or
foreign law, rule or regulation, no representation is made herein with respect
to any of the same applicable solely to the Subscriber and not to the Company.
The business of the Company is not being conducted in violation of any law,
ordinance or regulation of any governmental entity, in any manner that is
inconsistent with or in violation of the Certificate or By-laws, or in
violation of any material contract or agreement to which the Company is a
party, except for possible violations which either singly or in the aggregate
do not and will not have a Material Adverse Effect. The Company is not
required under federal, state or local law, rule or regulation in the United
States to obtain any consent, authorization or order of, or make any filing or
registration with, any court or governmental agency in order for it to execute,
deliver or perform any of its obligations under this Agreement, the
Registration Rights Agreement or any of the Securities or to issue and sell the
Securities in accordance with the terms hereof and thereof (other than any SEC,
NASD, Exchange or state securities filings which may be required to be made by
the Company from time to time, and any registration statement which may be
filed pursuant hereto); provided, that, for purposes of the representation made
in this sentence, the Company is assuming and relying upon the accuracy of the
relevant representations and agreements of the Subscriber herein.

3.9. Exchange Act Reports. The Company has delivered or made
available to the Subscriber true and complete copies of the Exchange Act
Reports (including, without limitation, proxy information and solicitation
materials). The Company has not provided to the Subscriber any information
which, according to applicable law, rule or regulation, should have been
disclosed publicly prior to the date hereof by the Company but which has not
been so disclosed. As of their respective dates, the Exchange Act Reports
complied in all material respects with the requirements of the Exchange Act and
rules and regulations of the SEC promulgated thereunder and other federal,
state and local laws, rules and regulations applicable to such Exchange Act
Reports, and none of the Exchange Act Reports contained any untrue statement of
a material fact or omitted to state a material fact required to be stated
therein or
<PAGE> 10
- 10 -

necessary in order to make the statements therein, in light of the
circumstances under which they were made, not misleading. The financial
statements of the Company included in the Exchange Act Reports comply as to
form in all material respects with applicable accounting requirements and the
published rules and regulations of the SEC or other applicable rules and
regulations with respect thereto. Such financial statements have been prepared
in accordance with generally accepted accounting principles applied on a
consistent basis during the periods involved (except (i) as may be otherwise
indicated in such financial statements or the notes thereto or (ii) in the case
of unaudited interim statements, to the extent they may not include footnotes
or may be condensed or summary statements) and fairly present in all material
respects the financial position of the Company as of the dates thereof and the
results of operations and cash flows for the periods then ended (subject, in
the case of unaudited statements, to normal year-end audit adjustments). As of
the Closing Date, the Company has filed all reports and is otherwise eligible
to effect registration of its Common Stock on Form S-3.

3.10. No Material Adverse Change. Since September 30, 1996, except
as set forth on Schedule 1.3, no event or circumstance has occurred or arisen
which has had or is reasonably likely to have a Material Adverse Effect on the
Company or its subsidiaries.

3.11. No Undisclosed Liabilities. The Company and its subsidiaries
have no liabilities or obligations which are material, individually or in the
aggregate, and are not disclosed in the Exchange Act Reports, other than those
incurred in the ordinary course of the Company's or its subsidiaries'
respective businesses since September 30, 1996, and which, individually or in
the aggregate, do not or would not have a Material Adverse Effect on the
Company or any of its subsidiaries.

3.12. No Undisclosed Events or Circumstances. No event or
circumstance has occurred or exists with respect to the Company or its
subsidiaries or their respective businesses, properties, prospects, operations
or financial condition, which, under applicable law, rule or regulation,
requires public disclosure or announcement prior to the date hereof by the
Company but which has not been so publicly announced or disclosed.

3.13. No Integrated Offering. Neither the Company, nor any of its
affiliates, nor any person acting on its or their behalf has, directly or
indirectly, at any time since December 1, 1995, made any offers or sales of any
security or solicited any offers to buy any security under circumstances that
would eliminate the availability of the exemption from registration under
Regulation D promulgated under the Securities Act in connection with the offer
and sale of the Securities as contemplated hereby.
<PAGE> 11
- 11 -

3.14. No Brokers. The Company has taken no action which would give
rise to any claim by any person for brokerage commissions, finder's fees or
similar payments by the Subscriber relating to this Agreement for the
transactions contemplated hereby, except for dealings with Promethean
Investment Group, L.L.C., whose fees will be paid for by the Subscriber.

4. COVENANTS OF THE COMPANY.

4.1. Registration Rights. The Company agrees that, at the Closing,
it will enter into the Registration Rights Agreement.

4.2. Reservation of Common Stock. As of the date hereof, the
Company has reserved and the Company shall continue to reserve and keep
available at all times, free of preemptive rights, shares of Common Stock for
the purpose of enabling the Company to satisfy any obligation to issue shares
of its Common Stock upon conversion of the Debentures (including Additional
Shares) or exercise of the Warrants; provided, however, that the number or
shares so reserved shall, except as provided herein and in the Debentures, not
exceed 4,761,230 shares, of which 250,000 shares shall be reserved, first, for
issuance upon exercise of the First Warrants and, second, for issuance upon
conversion of the Debentures (including Additional Shares) and upon exercise of
the Second Warrants if and to the extent the First Warrants expire unexercised.
The number of shares so reserved may be reduced by the number of shares
actually delivered pursuant to conversion of Debentures or exercise of the
Warrants (provided that in no event shall the number of shares so reserved be
less than the maximum number required to satisfy the remaining conversion
rights on the unconverted Debentures and the remaining exercise rights under
unexercised Warrants) and the number of shares so reserved shall be increased
to reflect stock splits, stock dividends and other distributions.

4.3. Listing of Underlying Shares. The Company hereby agrees,
promptly following the Closing, to take such action to cause the Shares to be
listed on the Exchange as promptly as possible but no later than 75 days
following the Closing. The Company further agrees, if the Company applies to
have the Common Stock traded on any other principal stock exchange or market,
it will include in such application the Shares and will take such other action
as is necessary or desirable to cause the Shares to be listed on such other
exchange or market as promptly as possible.

4.4. Exchange Act Registration. The Company will cause its Common
Stock to continue to be registered under Section 12(g) or 12(b) of the Exchange
Act, will comply in all respects with its reporting and filing obligations
under said Act, and will not take any action or file any document (whether or
not permitted by said Act or the rules thereunder) to terminate or suspend such
registration or to terminate or suspend its reporting and filing obligations
under said Act. The Company will
<PAGE> 12
- 12 -

take all action under its control to continue the listing and trading of its
Common Stock on the Exchange and will comply in all respects with the Company's
reporting, filing and other obligations under the bylaws or rules of the NASD
and the Exchange.

4.5. Legends. The Shares and certificates evidencing the same
shall, upon the effectiveness of the Registration Statement, be free of
legends, "stop transfers," "stock transfer restrictions," or other
restrictions, provided, that customary stock transfer restriction legends may
appear on any certificate evidencing any of such Shares if (a) a suspension
period pursuant to Section 8 of the Registration Rights Agreement or a market
standoff pursuant to Section 9 of the Registration Rights Agreement is then
applicable to such Shares, or (ii) the SEC or other governmental authority with
appropriate jurisdiction has issued an active stop order, injunction or other
order or requirement suspending the effectiveness of the Registration
Statement.

4.6. Corporate Existence. The Company will take all steps
necessary to preserve and continue the corporate existence of the Company.

4.7. Pledge Agreement. The Company agrees that, at the Closing, it
will enter into the Pledge Agreement.

5. LEGENDS.

5.1. Legends. The Company will issue one or more Debentures and
Warrants in the name of the Subscriber and in such denominations (but not less
than $50,000 each) to be specified by the Subscriber prior to (or from time to
time subsequent to) the Closing. The Debentures, the Warrants and certificates
evidencing any shares of Common Stock issued upon conversion or exercise
thereof prior to the effectiveness of the Registration Statement will bear the
following legend (the "Legend"):

Prior to Closing, the Company will issue to the transfer agent
for its Common Stock (and to any substitute or replacement transfer agent for
its Common Stock coterminous with the Company's appointment of any such
substitute or replacement transfer agent) instructions in substantially the
form and substance of the Transfer Agent Irrevocable Instruction in the form
attached as Exhibit D. Such
<PAGE> 13
- 13 -

instructions shall be irrevocable by the Company from and after the Closing or
from and after the issuance thereof to any such substitute or replacement
transfer agent, as the case may be. It is the intent and purpose of such
instructions, as provided therein, to require the transfer agent for the Common
Stock from time to time to issue certificates evidencing Shares free of the
Legend during the following periods and under the following circumstances and
without consultation by the transfer agent with the Company or its counsel and
without the need for any further advice or instruction to the transfer agent by
or from the Company or its counsel:

(a) At any time from and after the effectiveness of
the Registration Statement, and so long as (1) no suspension period
pursuant to Section 8 of the Registration Rights Agreement or market
stand-off pursuant to Section 9 of the Registration Rights Agreement
is then in effect, and (2) no stop order, injunction or other order of
the SEC or other applicable governmental authority with appropriate
jurisdiction is then in effect suspending effectiveness of the
Registration Statement:

(i) upon any surrender of one or more
Debentures or Warrants for conversion or exercise into Shares,
as the case may be;

(ii) upon any surrender of one or more
certificates evidencing Shares and which bear the Legend;

(b) At any time from and after the Closing Date, upon
any surrender of one or more certificates evidencing Shares and which
bear the Legend, to the extent accompanied by a notice requesting the
issuance of new certificates free of the Legend to replace those
surrendered and containing or also accompanied by representations that
(i) the Holder thereof is permitted to dispose thereof pursuant to
Rule 144(k) under the Securities Act or (ii) the Holder intends to
effect the sale or other disposition of such Stock, whether or not
pursuant to the Registration Statement, to a purchaser or purchasers
in a transaction not subject to the registration requirements of the
Securities Act, or (iii) such Holder is not then subject to such
requirements.

In addition, and if applicable, the Company shall reissue the
Debentures and Warrants without the Legend set forth above at such time as (i)
the Holder thereof is permitted to dispose thereof pursuant to Rule 144(k)
under the Act or (ii) the Holder intends to effect a sale thereof to a
purchaser or purchasers in a transaction not subject to the registration
requirements of the Act, or (iii) the Holder is not then subject to such
requirements.

5.2. No Other Legend or Stock Transfer Restrictions. No Legend has
been or shall be placed on the share certificates representing the Securities
and no instructions or "stop transfers," "stock transfer restrictions," or
other restrictions
<PAGE> 14
- 14 -

have been or shall be given to the Company's transfer agent with respect
thereto other than as set forth in this Section 5.

5.3. Subscriber's Compliance. Nothing in this section shall affect
in any way the Subscriber's obligations under and agreement to comply with all
applicable securities laws upon resale of the Securities.

6. OTHER ISSUANCES OF SECURITIES. During the period expiring 180
calendar days following the date the Registration Statement becomes effective,
the Company will not make any Equity Offerings, as defined in the Debentures,
pursuant to any exemption from the registration requirements of the Securities
Act of 1933, as amended, including without limitation the exemption provided by
Regulations S promulgated thereunder. Subject to the other provisions of this
Agreement, the Debentures and the Warrants, the restrictions on Equity
Offerings set forth in this Section 6 shall not prohibit the issuance of
securities by the Company pursuant to any bona fide corporate partnering
arrangement entered into by the Company, provided, that the Company shall
prohibit any Common Stock issued in connection with such corporate partnering
arrangements (and of Common Stock issuable upon exercise or conversion of any
debentures, warrants, options or other similar securities issued in connection
with such corporate partnering arrangements) from being sold or otherwise
transferred by the recipient thereof for a period of at least 180 days after
the closing date of such corporate partnering arrangements. As used herein,
the term "bona fide corporate partnering arrangement" shall mean any strategic
licensing, joint development, joint marketing or other similar cooperative
arrangement entered into by the Company with a corporation or other entity with
which the Company will have a continuing significant business relationship or a
subsidiary of such corporation or other entity other than as investor, on the
one hand, and issuer, on the other hand.

7. CHOICE OF LAW AND VENUE.

THIS AGREEMENT SHALL BE CONSTRUED UNDER THE LAWS OF THE STATE OF NEW YORK,
WITHOUT REGARD TO PRINCIPLES OF CONFLICTS OF LAW OR CHOICE OF LAW. The parties
hereby (i) irrevocably submits to the exclusive jurisdiction of the United
States District Court for the Southern District of New York for the purposes of
any suit, action or proceeding arising out of or relating to this Agreement and
(ii) waives, and agrees not to assert in any such suit, action or proceeding,
any claim that it is not personally subject to the jurisdiction of such court,
that the suit, action or proceeding is brought in an inconvenient forum or that
the venue of the suit, action or proceeding is improper. Each of the parties
consents to process being served in any such suit, action or proceeding by
mailing a copy thereof to such party at the address in effect for notices to it
under this Agreement and agrees that such service shall constitute good and
sufficient service of process and notice thereof. Nothing in this paragraph
shall affect or limit any right to serve process in any other manner permitted
by law.
<PAGE> 15
- 15 -

8. ASSIGNMENT; ENTIRE AGREEMENT; AMENDMENT.

8.1. Assignment. Neither this Agreement nor any rights of the
Subscriber hereunder may be assigned by either party to any other person.
Notwithstanding the foregoing, the provisions of this Agreement shall inure to
the benefit of, and be enforceable by, any transferee of any of the Securities
purchased or acquired by the Subscriber hereunder with respect to the
Securities held by such person.

8.2. Entire Agreement; Amendment. This Agreement, the Debentures,
the Warrants, the Registration Rights Agreement, the Pledge Agreement, and the
other documents delivered pursuant hereto constitute the full and entire
understanding and agreement between the parties with regard to the subjects
hereof and thereof, and no party shall be liable or bound to any other party in
any manner by any warranties, representations or covenants except as
specifically set forth in this Agreement or therein. Except as expressly
provided in this Agreement, neither this Agreement nor any term hereof may be
amended, waived, discharged or terminated other than by a written instrument
signed by the party against whom enforcement of any such amendment, waiver,
discharge or termination is sought.

9. PUBLICITY.

The Company agrees that it will not disclose, and will not
include in any public announcement, the name of the Subscriber without its
consent, unless and until such disclosure is required by law or applicable
regulation, and then only to the extent of such requirement and with the prior
approval of the Subscriber which the Subscriber agrees will not be unreasonably
withheld or delayed.

10. NOTICES, ETC.; EXPENSES; INDEMNITY.

10.1. Notices. Any notice, demand or request required or permitted
to be given by either the Company or the Subscriber pursuant to the terms of
this Agreement shall be in writing and shall be deemed to have been duly given
if personally delivered or sent by registered or certified mail, return receipt
requested, postage prepaid with a copy in each case sent on the same day to the
party by facsimile, Federal Express or other such expedited means to said party
at its address set forth at the end of this Agreement or such other address as
a party may request by notifying the other in writing and communications shall
be deemed to have been received when delivered personally or, if sent by mail
or facsimile, when actually received by the party to whom it is addressed.
Copies of all notices to the Subscriber shall be sent to its designee or
representative.

10.2. Indemnification. Each party shall indemnify the other against
any loss, cost or damages (including reasonable attorney's fees) incurred as a
result of such
<PAGE> 16
- 16 -

parties' breach of any representation, warranty, covenant or agreement in this
Agreement.

11. COUNTERPARTS.

This Agreement may be executed in any number of counterparts,
each of which shall be enforceable against the parties actually executing such
counterparts, and all of which together shall constitute one instrument.

12. SURVIVAL; SEVERABILITY.

The representations, warranties, covenants and agreements of the
parties hereto shall survive the Closing, provided that the representations and
warranties shall survive only until the third anniversary of the Closing. In
the event that any provision of this Agreement becomes or is declared by a
court of competent jurisdiction to be illegal, unenforceable or void, this
Agreement shall continue in full force and effect without said provision.

13. TITLE AND SUBTITLES.

The titles and subtitles used in this Agreement are used for
convenience only and are not to be considered in construing or interpreting
this Agreement.
<PAGE> 17
- 17 -

14. AMOUNT.

The undersigned Subscriber hereby subscribes for U.S. $_______ in
principal amount of Debentures and First Warrants to purchase
______________________ (_______) shares of Common Stock and agrees to pay
therefor funds in the amount of _____________________________ Dollars (U.S.
$________).

The undersigned acknowledges that this subscription shall not be
effective unless accepted by the Company as indicated below.

[THE REMAINDER OF THIS PAGE HAS BEEN INTENTIONALLY LEFT BLANK.]
<PAGE> 18
- 18 -

Subscriber's Representative: Name of Subscriber:

- ---------------------------- -------------------------------
Attn:

By
-----------------------------
Name:
Title:

Date of Subscription:
----------

Address:
Place of Execution:
------------

Telephone: Place of Organization or Citizenship:

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

Fax: Place of Residency and/or Principal
Place of Business:

Registration Instructions:

- ---------------------------- --------------------------------------
(Name)
(Please Print)
-------------

THIS SUBSCRIPTION IS ACCEPTED BY THE COMPANY ON THE 30TH DAY OF
DECEMBER, 1996.

ONCOR, INC.

By:
---------------------------------
Name:
--------------------------------
Title:
-------------------------------

<PAGE> 1

CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS

As independent public accountants, we hereby consent to the incorporation by
reference in this registration statement of our reports dated February 26, 1996,
included in Oncor, Inc.'s Form 10-K for the year ended December 31, 1995, and to
all references to our Firm included in this registration statement.

/s/ ARTHUR ANDERSEN LLP
------------------------
ARTHUR ANDERSEN LLP

Washington, D.C.
February 26, 1997