<PAGE>   1


                                                                   EXHIBIT 10.13


                              EMPLOYMENT AGREEMENT



     THIS AGREEMENT, made effective as of this 1st day of January, 1999, by and
between JACK KOGUT ("Employee") and NORTHFIELD LABORATORIES INC., a Delaware
corporation (the "Company").


                              W I T N E S S E T H :

     WHEREAS, Employee is now employed as the Vice President - Finance of the
Company;

     WHEREAS, the Company and Employee now desire to enter into this Agreement
in order to continue such employment for the term set forth herein and subject
to the terms and conditions set forth herein; and

     WHEREAS, the Company and Employee desire to continue the Proprietary
Information and Inventions Agreement entered into by and between Employee and
the Company dated October 1, 1986 (the "Proprietary Information and Inventions
Agreement") in full force and effect;

     NOW, THEREFORE, in consideration of the premises, and of the mutual
covenants hereinafter set forth, the parties do hereby agree as follows:

     1.   Employment. The Company agrees to employ Employee, and Employee agrees
to remain in the employ of the Company, for the period (the "Employment Period")
beginning on January 1, 1999 and ending on the earlier to occur of (a) December
31, 2000 or (b) the date as of which Employee's employment is terminated
pursuant to paragraph 5 of this Agreement. During the Employment Period,
Employee shall serve as the Vice President Finance of the Company and shall
perform such executive and managerial duties consistent with such position as
the Board of Directors of the Company shall from time to time direct. Employee
shall devote his best efforts to the business of the Company and its
subsidiaries.

     2.   Location. Employee shall be based at the Company's headquarters in
Evanston, Illinois, or at such other location as may be agreed upon by Employee
and the Board of Directors of the Company. Employee shall, however, also travel
to other locations at such times as may be appropriate for the performance of
his duties under this Agreement.

     3.   Compensation. During the Employment Period, Employee shall be
compensated as follows:

          (a)  Salary and Bonus. An "Employment Year" shall be the twelve-month
period beginning on the first day of the Employment Period and on each
anniversary of such date during the Employment Period. For the first Employment
Year, Employee shall be paid an annual base salary at a rate which is not less
than $219,772 per year. Employee's base salary shall be subject to review by the
Board of Directors of the Company and may only be adjusted upward each
Employment Year. Employee's base salary shall be paid in equal, semi-monthly
installments.

          (b)  Paid Vacation. Employee shall be entitled to 5 weeks paid
vacation in each calendar year. Any vacation which is not used by Employee will
be forfeited at the end of the calendar year.


                                      -27-
<PAGE>   2

          (c)  Expenses. Employee shall be reimbursed for all reasonable
business expenses incurred in the performance of his duties pursuant to this
Agreement, to the extent such expenses are substantiated and are consistent with
the general policies of the Company and its subsidiaries relating to the
reimbursement of expenses of senior executive officers.

          (d)  Fringe Benefits. In addition to any other compensation provided
under this Agreement, Employee shall also be entitled to participate, during the
Employment Period, in any and all pension, stock option, relocation, profit
sharing, and other employee benefit plans or fringe benefit programs which are
from time to time maintained by the Company or its subsidiaries for their senior
executive officers, in accordance with the provisions of such plans or programs
as from time to time in effect.

          (e)  Deduction and Withholding. All compensation and other benefits
payable to or on behalf of Employee pursuant to this Agreement shall be subject
to such deductions and withholding as may be agreed to by Employee or required
by applicable law.

     4.   Other Benefits. The compensation provisions of this Agreement shall
be in addition to, and not in derogation or diminution of, any benefits that
Employee or his beneficiaries may be entitled to receive under the provisions of
any pension, stock option, profit sharing, disability (except as otherwise
provided in subparagraph 6(b)), relocation or other employee benefit plan now or
hereafter maintained by the Company or by any of its subsidiaries. The Company
shall not make any changes in such plans or arrangements which would adversely
affect the Employee's rights or benefits thereunder, unless such change is made
uniformly in a plan of general application to all of the Company's or a
subsidiary's eligible employees.

     5.   Termination. The Employee's employment may be terminated without any
breach of this Agreement only under the following circumstances:

          (a)  Death. The Employee's employment shall terminate upon his death.

          (b)  Disability. If, as a result of the Employee's incapacity due to
physical or mental illness or accident, (i) the Employee shall have been absent
from his duties for the Company on a full-time basis for the entire period of
six consecutive months and (ii) within thirty days after written Notice of
Termination is given (which may occur before or after the end of such six-month
period) shall not have returned to the performance of his duties, the Company
may terminate the Employee's employment for "disability."

          (c)  Cause. The Company may terminate the Employee's employment
hereunder for "cause." For purposes of this Agreement, "cause" shall mean any
conduct by the Employee involving dishonesty or moral turpitude or any failure
by the Employee to comply with any material term of this Agreement, the
Proprietary Information and Inventions Agreement, or any similar agreement with
the Company to which Employee is a party, which conduct or failure is materially
injurious to the Company, monetarily or otherwise. Notwithstanding the
foregoing, the Employee shall not be deemed to have been terminated for cause
without (i) at least 60 days prior written notice from the Company to the
Employee setting forth the reasons for the Company's intention to terminate for
cause, (ii) an opportunity to cure the stated cause during the 60-day notice
period, and (iii) after all of the preceding procedures have been satisfied or
made available, delivery to the Employee of a Notice of Termination from the
Board of Directors of the Company finding that in the good faith opinion of such
Board of Directors, Employee was guilty of the conduct or of the failure
described



                                      -28-
<PAGE>   3

in the second sentence of this subparagraph, specifying the particulars in
detail, and that the Employee has failed to cure the stated cause.

          (d)  Termination by the Employee. The Employee may voluntarily
terminate his employment at any time. Employee's termination of employment shall
be for "good reason" if he voluntarily terminates his employment:

          (i)  within 90 days after a "change in control" (as defined below)
               of the Company for any reason;

         (ii)  at any time after a "change in control" of the Company because:


               A. he has been reassigned to a position of lesser rank or
                  status or to a location other than Evanston, Illinois,
                  without his consent; or

               B. his annual base salary has been reduced; or

               C. his benefits have been reduced (unless such reduction is
                  made uniformly in a plan of general application to all of
                  the Company's or a subsidiary's eligible employees);

        (iii)  because of a failure by the Company to comply with any material
               provision of this Agreement which has not been cured within ten
               days after written notice of such noncompliance has been given
               by the Employee to the Company; or

         (iv)  because of any purported termination of the Employee's
               employment by the Company which is not effected pursuant to a
               Notice of Termination satisfying the requirements of
               subparagraph 5(e) hereof (and for purposes of this Agreement no
               such purported termination shall be effective).


For purposes of this Agreement, a "change in control" shall mean a change in
control of a nature that would be required to be reported in response to Item
1(a) of the Current Report on Form 8-K, as in effect as of the date of this
Agreement, promulgated pursuant to Section 13 or 15(d) of the Securities
Exchange Act of 1934, as amended (the "Exchange Act"), whether or not the
Company is then subject to the reporting requirements of the Exchange Act;
provided that, without limitation, such a change in control shall be deemed to
have occurred if (i) there shall be consummated any sale, lease, exchange or
other transfer (in one transaction or a series of related transactions) of all
or substantially all of the Company's assets, (ii) the stockholders of the
Company approve any plan or proposal of liquidation or dissolution of the
Company, (iii) there shall be consummated any consolidation or merger of the
Company in which the Company is not the surviving or continuing corporation, or
pursuant to which shares of the Company's Common Stock would be converted into
cash, securities or other property, other than a merger of the Company in which
the holders of the Company's Common Stock immediately prior to the merger have,
directly or indirectly, at least an 80% ownership interest in the outstanding
Common Stock of the surviving corporation immediately after the merger, (iv) any
"person" or "group" (as such terms are used in Section 13(d) and 14(d) of the
Exchange Act) becomes the "beneficial owner" (as defined in Rule 13d-3 under the
Exchange Act), directly or indirectly, of securities of the Company representing
30% or more of the combined voting power of

                                      -29-
<PAGE>   4

the Company's then outstanding voting securities ordinarily having the right to
vote for the election of directors (unless such acquisition of beneficial
ownership is approved by a majority of the Incumbent Board (as defined in clause
(v) below)) or (v) individuals who, as of the date of this Agreement, constitute
the Board of Directors of the Company (the "Board" generally, and as of the date
hereof, the "Incumbent Board") cease for any reason to constitute a majority of
the Board, provided that any person becoming a director subsequent to the date
of this Agreement whose election, or nomination for election by the Company's
stockholders, was approved by a vote of at least three-quarters of the directors
comprising the Incumbent Board (other than an election or nomination of an
individual whose initial assumption of office is in connection with an actual or
threatened election contest relating to the directors of the Company, as such
terms are used in Rule 14a-11 of Regulation 14A promulgated under the Exchange
Act) shall be, for purposes of this Agreement, considered as though such person
were a member of the Incumbent Board. Notwithstanding the foregoing, a public or
private sale or issuance of equity securities, or securities exercisable or
exchangeable for or convertible into equity securities, of the Company for its
own account or for the account of any holder of the Company's equity securities
as of the date hereof shall not result in a "change in control" for purposes of
this Agreement if such sale or issuance is approved by at least three-quarters
of the directors comprising the Incumbent Board.

          (e)  Notice of Termination. Any termination of the Employee's
employment by the Company or by the Employee (other than termination because of
the Employee's death) shall be communicated by written Notice of Termination to
the other party hereto. For purposes of this Agreement, a "Notice of
Termination" shall mean a notice which shall indicate the specific termination
provision of this Agreement relied upon and shall set forth in reasonable detail
the facts and circumstances claimed to provide a basis for termination of the
Employee's employment under the provision so indicated.

          (f)  Date of Termination of Employment. "Date of Termination" shall
mean (i) if the Employee's employment is terminated by his death, the date of
his death; (ii) if the Employee's employment is terminated for disability
pursuant to subparagraph 5(b) above, thirty days after Notice of Termination is
given (provided that the Employee shall not have returned to the performance of
his duties during such thirty-day period); (iii) if the Employee's employment is
terminated for any other reason, the date specified in the Notice of Termination
which shall not be less than 10 days nor more than 60 days from the date Notice
of Termination is given; provided that if within thirty days after any Notice of
Termination is given the party receiving such Notice of Termination notifies the
other party that a dispute exists concerning the termination, the Date of
Termination shall be the date on which the dispute is finally determined, either
by mutual written agreement of the parties, by a binding and final arbitration
award or by a final judgment, order or decree of a court of competent
jurisdiction (the time for appeal therefrom having expired and no appeal having
been perfected).

     6.   Compensation Upon Termination of Employment or During Disability.

          (a)  Death. If the Employee's employment is terminated by his death,
the Company shall continue to pay his full base salary at the rate than in
effect to the Employee's surviving spouse or, if he has no surviving spouse, to
his estate as a death benefit for a period of one (1) month following his Date
of Termination.

          (b)  Disability. During any period that the Employee fails to perform
his duties hereunder as a result of incapacity due to physical or mental illness
or accident, the Company shall continue to pay him his full base salary at the
rate then in effect for such period until his Date of


                                      -30-
<PAGE>   5

Termination. Notwithstanding the preceding sentence any salary payments made to
the Employee during such period of incapacity shall be reduced (but not below
zero) by amounts actually paid to the Employee for the same period and at or
prior to the time of any such salary payment under disability benefit plans
maintained by the Company; provided such disability benefit amounts were not
previously applied to reduce any such salary payment.


          (c)  Cause. If the Employee's employment is terminated for cause, the
Company shall pay the Employee his full base salary through the Date of
Termination at the rate in effect at the time Notice of Termination is given
and, except for other compensation or benefits accrued through his Date of
Termination, the Company shall have no further obligations to the Employee under
this Agreement except as otherwise required by applicable law.

          (d)  Breach; Termination for Good Reason. If (i) in breach of this
Agreement, the Company shall terminate the Employee's employment other than
pursuant to subparagraphs 5(a), 5(b) or 5(c) hereof (it being understood that a
purported termination pursuant to subparagraphs 5(b) or 5(c) hereof which is
disputed and finally determined not to have been proper shall be a termination
of the Employee's employment by the Company in breach of this Agreement) or (ii)
the Employee shall terminate his employment for good reason, then:

               A.   the Company shall continue to pay the Employee his full base
                    salary at a rate equal to 100 percent of the annual rate in
                    effect prior to the date Notice of Termination is given
                    until the later to occur of December 31, 2000 or the second
                    anniversary of his Date of Termination, such payments of
                    continued base salary will be reduced (but not below zero)
                    by any payments made by the Company under the Proprietary
                    Information and Inventions Agreement.

               B.   During the period that Employee is entitled to receive
                    payments of continued base salary under A. above, Employee
                    shall continue to participate in any accident, health,
                    disability, life or similar employee welfare benefit plans
                    maintained by the Company or its subsidiaries, to the extent
                    he was eligible to participate in such plans at any time
                    during the twelve months preceding his Notice of Termination
                    and at no cost to him; provided that if such continued
                    participation is precluded by the provisions of such plans
                    or by applicable law, the Company will provide Employee with
                    comparable benefits of equivalent value.


               C.   Employee understands and agrees that if he breaches any
                    provision of the Proprietary Information and Inventions
                    Agreement, the Company shall cease to have any obligation to
                    make any payment under this subparagraph 6(d).

          (e)  Voluntary Termination. If the Employee voluntarily terminates his
employment other than for good reason, he shall not be entitled to receive any
compensation or benefits pursuant to this Agreement other than compensation or
benefits accrued through the Date of Termination.


                                      -31-
<PAGE>   6

          (f)  Severance. If Employee does not continue in employment with the
Company after December 31, 2000 for a reason other than Employee's death,
disability or discharge for cause, the Company shall continue to pay Employee
his full base salary, at a rate equal to the rate in effect immediately prior to
December 31, 2000, until December 31, 2001. Employee shall not be entitled to
receive any severance payments under this subparagraph 6(f) if (i) Employee is
not employed by the Company immediately prior to December 31, 2000, or (ii)
Employee is entitled to receive any benefits under subparagraph 6(d) above.
Severance payments will be reduced (but not below zero) by any payments made
under the Proprietary Information and Inventions Agreement. Employee understands
and agrees that if he breaches any provision of the Proprietary Information and
Inventions Agreement, the Company shall cease to have any obligation to make any
severance payments under this subparagraph.

          (g)  Mitigation. The Employee shall not be required to mitigate the
amount of any payment provided for this paragraph 6 by seeking other employment
or otherwise, nor shall the amount of any payments provided in this Agreement be
reduced by any compensation earned by Employee as the result of his
self-employment or his employment by another employer after his Date of
Termination.

     7.   Successors; Binding Agreement.

          (a)  Successors to the Company. The Company will require any successor
(whether direct or indirect, by purchase, merger, consolidation or otherwise) to
all or substantially all of the business and/or assets of the Company, by
agreement in form and substance satisfactory to the Employee, to expressly
assume and agree to perform this Agreement in the same manner and to the same
extent that the Company would be required to perform it if no such succession
had taken place. Failure of the Company to obtain such agreement prior to the
effectiveness of any such succession shall be a breach of this Agreement and
shall entitle the Employee to terminate his employment with the Company for good
reason. As used in this Agreement, "Company" shall mean the Company and any
successor to its business and/or assets which executes and delivers the
agreement provided for in this paragraph 7 or which otherwise becomes bound by
all the terms and provisions of this Agreement by operation of law.

          (b)  Assignment. Employee's rights and interests under this Agreement
may not be assigned, pledged or encumbered by him without the Company's written
consent. This Agreement and all rights of the Employee hereunder shall inure to
the benefit of and be enforceable by the Employee's personal or legal
representatives, executors, administrators, successors, heirs, distributees,
devisees and legatees. If the Employee should die while any amounts would still
be payable to him hereunder if he had continued to live all such amounts, unless
otherwise provided herein, shall be paid in accordance with the terms of this
Agreement to the Employee's surviving spouse or, if there is no surviving
spouse, to his estate.

     8.   Proprietary Information. Employee and the Company have entered into
the Proprietary Information and Inventions Agreement, which agreement shall
remain in full force and effect.

     9.   Payment of Costs and Indemnification.

          (a)  Payment of Costs. In the event that a dispute arises regarding
termination of Employee's employment or the interpretation or enforcement of
this Agreement and Employee obtains

                                      -32-
<PAGE>   7

a final judgment in his favor from a court of competent jurisdiction from which
no appeal may be taken, whether because the time to do so has expired or
otherwise, or his claim is settled by the Company prior to the rendering of such
a judgment, the Company shall promptly pay, or reimburse to Employee, all
reasonable legal fees and expenses incurred by Employee in contesting or
disputing any such termination, in seeking to obtain or enforce any right or
benefit provided for in this Agreement, or in otherwise pursuing his claim.

          (b)  Indemnification. The Company shall indemnify and hold Employee
harmless to the maximum extent permitted by law against judgments, fines,
amounts paid in settlement and reasonable expenses, including attorneys' fees,
incurred by Employee in connection with the defense of, or as a result of, any
action or proceeding (or any appeal from any action or proceeding) in which
Employee is made or is threatened to be made a party by reason of the fact that
Employee is or was an employee, officer, or director of the Company or any of
its subsidiaries, regardless of whether such action or proceeding is one brought
by or in the right of the Company to procure a judgment in its favor. The
undertaking of subparagraph (a) above is independent of, and shall not be
limited or prejudiced by, the undertakings of this subparagraph (b).

          (c)  Warranty. The Company hereby represents and warrants that the
undertakings of payment and indemnification set out in (a) and (b) above are not
in conflict with the Certificate of Incorporation or by-laws of the Company or
with any validly existing agreement or other proper corporate action of the
Company.

     10.  General Provisions.

          (a)  Effect of Headings. The headings of all of the paragraphs and
subparagraphs of this Agreement are inserted for convenience of reference only
and shall not affect the construction or interpretation of this Agreement.

          (b)  Modification, Amendment, Waiver. No modification, amendment, or
waiver of any provision of this Agreement shall be effective unless approved in
writing by both parties. The failure at any time to enforce any of the
provisions of this Agreement shall in no way be construed as a waiver of such
provisions and shall not affect the right of either party thereafter to enforce
each and every provision of this Agreement in accordance with its terms.

          (c)  Severability. Whenever possible, each provision of this Agreement
shall be interpreted in such manner as to be effective and valid under
applicable law, but if any provision of this Agreement shall be held to be
prohibited by or invalid under applicable law, such provision shall be
ineffective only to the extent of such prohibition or invalidity, without
invalidating the remainder of such provision or the remaining provisions of this
Agreement.

          (d)  No Strict Construction. The language used in this Agreement shall
be deemed to be the language chosen by the parties hereto to express their
mutual intent, and no rule of strict construction shall be applied against any
person.

          (e)  Choice of Law. All questions concerning the construction,
validity and interpretation of this Agreement shall be governed by the laws of
the State of Illinois.

          (f)  Notices. Any notice to be served under this Agreement shall be in
writing and shall be mailed by registered mail, return receipt requested,
addressed:

                                      -33-
<PAGE>   8

          If to the Company, to:
          Northfield Laboratories Inc.
          1560 Sherman Avenue
          Evanston, Illinois  60201-4800
          Attention:  Board of Directors

          If to Employee, to:
          Jack Kogut
          903 South Kennicott Place
          Mt. Prospect, Illinois 60056-4073

or to such other place as either party may specify in writing, delivered in
accordance with the provisions of this subparagraph.

          (g)  Survival. The rights and obligations of the parties shall survive
the term of Employee's employment to the extent that any performance is required
under this Agreement after the expiration or termination of such term.

          (h)  Entire Agreement. This Agreement, together with the Proprietary
Information and Inventions Agreement described in paragraph 8 above, constitutes
the entire agreement of the parties with respect to the subject matter thereof,
and supersedes all previous agreements between the parties relating to the same
subject matter (but excluding the Proprietary Information and Inventions
Agreement, which agreement shall remain in full force and effect).










                                      -34-
<PAGE>   9


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

     11.  Parachute Payment Adjustment. If the Company, in good faith,
determines that any part or all of the amounts payable to Employee pursuant to
this Agreement would be "excess parachute payments" within the meaning of
Section 280G(b) of the Internal Revenue Code of 1986, as amended (the "Code"),
the Company may, in its discretion, reduce the amounts so payable so that the
aggregate present value of such amounts will be less than 3 times the Employee's
"base amount" as defined in Section 280G(b)(3) of the Code.

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement
effective as of the day and year first above written.


EMPLOYEE                                           NORTHFIELD LABORATORIES INC.


                                                   By
----------------------------                         ------------------------
Jack Kogut                                         Its
                                                      -----------------------






























                                      -35-