Exhibt 10.15

                              SPECTRASCIENCE, INC.


                   WARRANT TO PURCHASE SHARES OF COMMON STOCK*
          Void After Midnight, Central Standard Time, December 28, 1999


No. PB122898-_____

         This is to certify that, for value received, _________________________
(the "Holder") is entitled to purchase, subject to the provisions of this
Warrant, from SPECTRASCIENCE, Inc., a Minnesota corporation (the "Company"), at
any time from and after the date hereof and prior to December 28, 1999, (the
"Exercise Period"), fully paid non-assessable shares of the Common Stock,
twenty-five cent par value, of the Company ("Common Stock"), exercisable at the
purchase price per share of $6.00, subject to the provisions of this Warrant.
The number of shares subject to exercise under this warrant shall be equivalent
to the number of shares of Common Stock purchased by exercising that certain
warrant, PB122895-____, dated December 28, 1995, as amended December 28, 1998.
The number of shares of Common Stock to be received upon the exercise of this
Warrant and the price to be paid for a share of Common Stock may be adjusted
from time to time as hereinafter set forth. The shares of Common Stock
deliverable upon such exercise, and as adjusted from time to time, are
hereinafter sometimes referred to as "Warrant Stock" and the exercise price of a
share of Common Stock in effect at any time and as adjusted from time to time,
is hereinafter sometimes referred to as the "Exercise Price." This Warrant is
one of a series of Warrants, identical in form, which may be issued by the
Company to purchase shares of Common Stock of the Company; and the term
"Warrants" as used herein means all such warrants (including this Warrant).

1. EXERCISE OF WARRANT. This Warrant may be exercised in whole or in part, at
any time or from time to time, during the Exercise Period, but not later than
Midnight, Central Standard Time, on December 28, 1999, by presentation and
surrender to the Company or its stock transfer agent, if any, together with the
Exercise Form attached hereto, duly executed, and payment of the Exercise Price
for the number of shares specified in such form along with all federal and state
taxes applicable upon such exercise. If December 28, 1999 is a day on which
banking institutions are authorized by law to close, this Warrant may then be
exercised on the first day thereafter which shall not be such a day. If this
Warrant should be exercised in part only, the Company shall, upon surrender of
this Warrant for cancellation, execute and deliver a new Warrant evidencing the
right of the Holder to purchase the balance of the shares purchasable hereunder.
Upon receipt by the Company of this Warrant at the office or agency of the
Company, in proper form for exercise, the Holder shall be deemed to be the
Holder of record of the shares of Common Stock issuable upon such exercise,
notwithstanding that the stock transfer books of the Company shall then be
closed or that certificates representing such shares of Common Stock shall not
then be actually delivered to the Holder.


--------------------------------------------------------------------------------
    *THIS WARRANT IS SUBJECT TO THE RESTRICTIONS ON TRANSFER SET FORTH AT THE
                        BOTTOM OF THE LAST PAGE HEREOF.

<PAGE>


2. RESERVATION OF SHARES. The Company hereby agrees that at all times there
shall be reserved for issuance and/or delivery upon exercise of this Warrant
such number of shares of Common Stock as shall be required for issuance or
delivery upon the exercise of this Warrant.

3. FRACTIONAL SHARES. No fractional shares or scrip representing fractional
shares shall be issued upon the exercise of this Warrant. With respect to any
fraction of a share called for upon any exercise hereof, the Company shall pay
to the Holder an amount in cash equal to such fraction multiplied by the current
market value of such fractional share, determined as follows:

     3.1 If the Common Stock is listed on a national securities exchange or
     admitted to unlisted trading privileges on such exchange, the current value
     shall be the last reported sale price of the Common Stock on such exchange
     on the last business day prior to the date of exercise of this Warrant. If
     no sale is made on such day, the current value shall be the average of the
     closing bid and asked prices for such day on such exchange; or

     3.2 If the Common Stock is not listed on a national securities exchange or
     admitted to unlisted trading privileges, the current value shall be the
     mean of the last reported bid and asked prices reported by the National
     Association of Securities Dealers Quotation System (or, if not so quoted on
     NASDAQ, by the National Quotation Bureau, Inc.) on the last business day
     prior to the date of the exercise of this Warrant; or

     3.3 If the Common Stock is not listed on a national securities exchange or
     admitted to unlisted trading privileges, and bid and asked prices are not
     so reported, the current value shall be an amount, not less than book
     value, determined in such reasonable manner as may be prescribed by the
     Board of Directors of the Company. Such determination will be final and
     binding on the Holder.

4. EXCHANGE, ASSIGNMENT OR LOSS OF WARRANT. Subject to Section 7, this Warrant
is exchangeable, without expense, at the option of the Holder, upon presentation
and surrender hereof to the Company, for other Warrants of different
denominations entitling the Holder thereof to purchase in the aggregate, the
same number of shares of Common Stock purchasable hereunder. Any such assignment
shall be made by surrender of this Warrant together with the Assignment Form
attached hereto, duly executed, and funds sufficient to pay any transfer tax.
The Company shall, without change, execute and deliver a new Warrant in the name
of the assignee named in such instrument of assignment and this Warrant shall
promptly be canceled. This Warrant may be divided or combined with other
Warrants which carry the same rights, upon surrender hereof of all affected
Warrants, at the office of the Company or its stock transfer agent, if any,
together with a written notice, signed by the Holder of such affected Warrants,
specifying the names and denominations in which new Warrants are to be issued.
The term "Warrant" as used herein includes any Warrants issued in substitution
for or replacement of this Warrant, or into which this Warrant may be divided or
exchanged. Upon receipt by the Company of evidence satisfactory to it of the
loss, theft, destruction or mutilation of this Warrant, and of reasonably
satisfactory indemnification in the case of loss, theft or destruction, or upon
surrender and cancellation of this Warrant if mutilated, the Company will
execute and deliver a new Warrant of like tenor and date. Any such new Warrant
executed and delivered shall constitute an additional contractual obligation on
the part of the Company, whether or not


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<PAGE>


this Warrant is lost, stolen, destroyed or mutilated, and shall be enforceable
at any time by anyone.

5. RIGHTS OF THE HOLDER. The Holder shall not, by virtue hereof, be entitled to
any rights of a shareholder in the Company, either at law or equity, and the
rights of the Holder are limited to those expressed in the Warrant and are not
enforceable against the Company, either at law or equity, except to the extent
set forth herein.

6. STOCK SPLITS, REORGANIZATION, MERGER, SALE OF ALL ASSETS.

     6.1 In case the Company shall declare any dividend or other distribution
     upon its outstanding common stock payable in common stock, or shall
     subdivide its outstanding shares of common stock into a greater number of
     shares, then the number of shares of common stock which may thereafter be
     purchased upon the exercise of the rights represented hereby, shall be
     increased in proportion to the increase through such dividend or
     subdivision and the purchase price per share shall be decreased in such
     proportion. In case the Company shall at any time combine the outstanding
     shares of its common stock into a smaller number of shares, the number of
     shares of common stock which may thereafter be purchased upon the exercise
     of the rights represented hereby, shall be decreased in proportion to the
     decrease through such combination and the purchase price per share shall be
     increased in such proportion.

     6.2 In case of any reclassification, capital reorganization or other change
     of outstanding shares of Common Stock of the Company (other than a change
     in par value, or from without par value to par value, or from par value to
     without par value, or as a result of an issuance of Common Stock by way of
     dividend or other distribution or of a subdivision or combination), or in
     case of any consolidation or merger of the Company with or into another
     corporation (other than a merger with a subsidiary in which merger the
     Company is the continuing corporation and which does not result in any
     reclassification, capital reorganization or other change of outstanding
     shares of Common Stock of the class issuable upon exercise of this Warrant)
     or in case of any sale or conveyance to another corporation of the property
     of the Company as an entirety or substantially as an entirety, the Company
     shall cause an effective provision to be made so that the Holder shall have
     the right thereafter, by exercising this Warrant, to purchase the kind and
     amount of shares of stock and other securities and property receivable upon
     such reclassification, capital reorganization or other change,
     consolidation, merger, sale or conveyance, if any, which the Holder would
     have received had the Warrants been exercised immediately prior to such
     event.

              The Company shall not effect any such consolidation, merger, or
     sale, unless prior to or simultaneously with the consummation thereof, the
     successor corporation (if other than the Company) resulting from such
     consolidation or merger or the corporation purchasing such assets shall
     assume by written instrument executed and mailed or delivered to the Holder
     at the last address of such Holder appearing on the books of the Company,
     the obligation to deliver to such Holder such shares of stock, securities
     or assets as, in accordance with the foregoing provisions, such Holder may
     be entitled to purchase.


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7. TRANSFER TO COMPLY WITH THE SECURITIES ACT OF 1933

     7.1 This Warrant or the Warrant Stock or any other security issued or
     issuable upon exercise of this Warrant may not be offered or sold except in
     conformity with the Securities Act of 1933, as amended, and then, only
     against receipt of an agreement from the person to whom such offer of sale
     is made to comply with the provisions of this Section 7.1 with respect to
     any resale or other disposition of such securities.

     7.2 The Company may cause the following legend to be set forth on each
     Warrant and certificate representing Warrant Stock or any other security
     issued or issuable upon exercise of this Warrant not theretofore
     distributed to the public or sold to underwriters for distribution to the
     public unless counsel for the Company is of the opinion as to any such
     certificate that such legend is unnecessary:

                  The securities represented by this certificate may not be
                  offered for sale, sold or otherwise transferred except
                  pursuant to an effective registration statement made under the
                  Securities Act of 1933 ("the Act"), or pursuant to an
                  exemption from registration under the Act.

8. REGISTRATION RIGHTS

     8.1 If the Company proposes to claim an exemption under Section 3(b) for a
     public offering of any of its securities or to register under the
     Securities Act of 1933 (except by a claim of exemption or registration
     statement on a form that does not permit the inclusion of shares by its
     security holders) any of its securities, it will give written notice to all
     registered holders of Warrants, and all registered holders of shares of
     common stock acquired upon the exercise of Warrants, of its intention to do
     so and, on the written request of any such registered holders given within
     twenty (20) days after receipt of any such notice (which request must be
     made within five (5) years from the date of this Warrant), the Company will
     use its best efforts to cause all such shares, the registered holders of
     which shall have requested the registration or qualification thereof, to be
     included in such notification or registration statement proposed to be
     filed by the Company; provided, however, that nothing herein shall prevent
     the Company from, at any time, abandoning or delaying any such registration
     initiated by it. If any such registration shall be underwritten in whole or
     in part, the Company may require that the shares requested for inclusion
     pursuant to this section be included in the underwriting on the same terms
     and conditions as the securities otherwise being sold through the
     underwriters. In the event that, in the good faith judgment of the managing
     underwriter of such public offering, the inclusion of all of the shares
     originally covered by a request for registration would reduce the number of
     shares to be offered by the Company or interfere with the successful
     marketing of the shares of stock offered by the Company, the number of
     shares otherwise to be included pursuant to this Section in the
     underwritten public offering may be reduced. Those shares which are thus
     excluded from the underwritten public offering shall be withheld from the
     market for a period, not to exceed 90 days, which the managing underwriter
     reasonably determines is necessary in order to effect the underwritten
     public offering. All expenses of such offering, except the fees of special
     counsel to such holders and brokers' commissions or underwriting discounts
     payable by such holders, shall be borne by the Company.


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     8.2 Further, on one occasion only, commencing one year from the date
     hereof, upon request by the holders of Warrants and/or the holders of
     shares issued upon the exercise of the Warrants who collectively (i) have
     the right to purchase at least 50% of the shares subject to the Warrants,
     (ii) hold directly at least 50% of the shares purchased hereunder, or (iii)
     have the right to purchase or hold directly an aggregate of at least 50% of
     the shares purchasable or purchased hereunder, the Company will promptly
     take all necessary steps, at the option of such holders, to register or
     qualify the sale of the Warrants or such shares by the holders thereof, or
     to register the issuance by the Company of shares upon the exercise of
     Warrants, under the Securities Act of 1933 (and, upon the request of such
     holders, under Rule 415 thereunder) and such state laws as such holders may
     reasonably request; provided that (i) such request must be made by December
     28, 2003, and (ii) the Company may delay the filing of any registration
     statement requested pursuant to this section to a date not more than ninety
     (90) days following the date of such request if in the opinion of the
     Company's principal investment banker at the time of such request such a
     delay is necessary in order not to adversely affect financing efforts then
     underway at the Company or if in the opinion of the Company such a delay is
     necessary or advisable to avoid disclosure of material nonpublic
     information. The costs and expenses directly related to any registration
     requested pursuant to this section, including but not limited to legal fees
     of the Company's counsel, audit fees, printing expense, filing fees and
     fees and expenses relating to qualifications under state securities or blue
     sky laws incurred by the Company shall be borne entirely by the Company;
     provided, however, that the persons for whose account the securities
     covered by such registration are sold shall bear the expenses of
     underwriting commissions applicable to their shares and fees of their legal
     counsel. If the holders of Warrants and the holders of shares of Common
     Stock underlying the Warrants are the only persons whose shares are
     included in the registration pursuant to this section, such holders shall
     bear the expense of inclusion of audited financial statements in the
     registration statement which are not dated as of the Company's normal
     fiscal year or are not otherwise prepared by the Company for its own
     business purposes. The Company shall keep effective and maintain any
     registration, qualification, notification or approval specified in this
     paragraph for such period as may be necessary for the holders of the
     Warrants and such common stock to dispose thereof, and from time to time
     shall amend or supplement, at the holder's expense, the prospectus or
     offering circular used in connection therewith to the extent necessary in
     order to comply with applicable law, provided that the Company shall not be
     obligated to maintain any registration for a period of more than nine (9)
     months.

              If, at the time any written request for registration is received
     by the Company pursuant to this Section 8.2, the Company has determined to
     proceed with the actual preparation and filing of a registration statement
     under the Securities Act in connection with the proposed offer and sale for
     cash of any of its securities by it or any of its security holders, such
     written request shall be deemed to have been given pursuant to Section 8.1
     hereof rather than this Section 8.2, and the rights of the holders of
     Warrants and or shares issued upon the exercise of the Warrants covered by
     such written request shall be governed by Section 8.1 hereof.

              The managing underwriter of an offering registered pursuant to
     this Section 8.2, if any, shall be selected by the holders of a majority of
     the Warrants and/or shares issued upon


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<PAGE>


     the exercise of the Warrants for which registration has been requested and
     shall be reasonably acceptable to the Company. Without the written consent
     of the holders of a majority of the Warrants and/or shares issued upon
     exercise of the Warrants for which registration has been requested
     pursuant to this Section 8.2, neither the Company nor any other holder of
     securities of the Company may include securities in such registration if
     in the good faith judgment of the managing underwriter of such public
     offering the inclusion of such securities would interfere with the
     successful marketing of the Warrants and/or shares issued upon the
     exercise of the Warrants or require the exclusion of any portion of the
     Warrants and/or shares issued upon the exercise of the Warrants to be
     registered. Subject to the preceding sentence, shares to be excluded from
     an underwritten public offering shall be selected in the manner provided
     in Section 8.1 hereof.

     8.3 If and whenever the Company is required by the provisions of Sections
     8.1 or 8.2 hereof to effect the registration of Warrants and/or shares
     issued upon the exercise of the Warrants under the Securities Act, the
     Company will:

                      (i) prepare and file with the Commission a registration
              statement with respect to such securities, and use its best
              efforts to cause such registration statement to become and remain
              effective for such period as may be reasonably necessary to effect
              the sale of such securities;

                      (ii) prepare and file with the Commission such amendments
              to such registration statement and supplements to the prospectus
              contained therein as may be necessary to keep such registration
              statement effective for such period as may be reasonably necessary
              to effect the sale of such securities;

                      (iii) furnish to the security holders participating in
              such registration and to the underwriters of the securities being
              registered such reasonable number of copies of the registration
              statement, preliminary prospectus, final prospectus and such other
              documents as such underwriters may reasonably request in order to
              facilitate the public offering of such securities;

                      (iv) use its best efforts to register or qualify the
              securities covered by such registration statement under such state
              securities or blue sky laws of such jurisdictions as such
              participating holders may reasonably request in writing within 30
              days following the original filing of such registration statement,
              except that the Company shall not for any purpose be required to
              execute a general consent to service of process or to qualify to
              do business as a foreign corporation in any jurisdiction wherein
              it is not so qualified;

                      (v) notify the security holders participating in such
              registration, promptly after it shall receive notice thereof, of
              the time when such registration statement has become effective or
              a supplement to any prospectus forming a part of such registration
              statement has been filed;


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                  (vi) notify such holders promptly of any request by the
            Commission for the amending or supplementing of such registration
            statement or prospectus or for additional information;

                  (vii) prepare and file with the Commission, promptly upon the
            request of any such holders, any amendments or supplements to such
            registration statement or prospectus which, in the opinion of
            counsel for such holders (and concurred in by counsel for the
            Company), is required under the Securities Act or the rules and
            regulations thereunder in connection with the distribution of the
            Warrants or shares by such holder;

                  (viii) prepare and promptly file with the Commission and
            promptly notify such holders of the filing of such amendment or
            supplement to such registration statement or prospectus as may be
            necessary to correct any statements or omissions if, at the time
            when a prospectus relating to such securities is required to be
            delivered under the Securities Act, any event shall have occurred as
            the result of which any such prospectus or any other prospectus as
            then in effect would include an untrue statement of a material fact
            or omit to state any material fact necessary to make the statements
            therein, in the light of the circumstances in which they were made,
            not misleading;

                  (ix) advise such holders, promptly after it shall receive
            notice or obtain knowledge thereof, of the issuance of any stop
            order by the Commission suspending the effectiveness of such
            registration statement or the initiation or threatening of any
            proceeding for that purpose and promptly use its best efforts to
            prevent the issuance of any stop order or to obtain its withdrawal
            if such stop order should be issued;

                  (x) not file any amendment or supplement to such registration
            statement or prospectus to which a majority in interest of such
            holders shall have reasonably objected on the grounds that such
            amendment or supplement does not comply in all material respects
            with the requirements of the Securities Act or the rules and
            regulations thereunder, after having been furnished with a copy
            thereof at least five business days prior to the filing thereof,
            unless in the opinion of counsel for the Company the filing of such
            amendment or supplement is reasonably necessary to protect the
            Company from any liabilities under any applicable federal or state
            law and such filing will not violate applicable law; and

                  (xi) at the request of any such holder, furnish on the
            effective date of the registration statement and, if such
            registration includes an underwritten public offering, at the
            closing provided for in the underwriting agreement: (i) opinions,
            dated such respective dates, of the counsel representing the Company
            for the purposes of such registration, addressed to the
            underwriters, if any, and to the holder or holders making such
            request, covering such matters as such underwriters and holder or
            holders may reasonably request; and (ii) letters, dated such
            respective dates, from the independent certified public accountants
            of the Company, addressed to the underwriters, if any, and to the
            holder or holders making such request, covering such matters as such
            underwriters and holder or holders may reasonably request, in which


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            letter such accountants shall state (without limiting the generality
            of the foregoing) that they are independent certified public
            accountants with the meaning of the Securities Act and that in the
            opinion of such accountants the financial statements and other
            financial data of the Company included in the registration statement
            or the prospectus or any amendment or supplement thereto comply in
            all material respects with the applicable accounting requirements of
            the Securities Act.

     8.4 The Company hereby indemnifies the holder of this Warrant and of any
     common stock issued or issuable hereunder, its officers and directors, and
     any person who controls such Warrant holder or such holder of common stock
     within the meaning of Section 15 of the Securities Act of 1933, against all
     losses, claims, damages and liabilities caused by any untrue statement of a
     material fact contained in any registration statement, prospectus,
     notification or offering circular (and as amended or supplemented if the
     Company shall have furnished any amendments or supplements thereto) or any
     preliminary prospectus or caused by any omission to state therein a
     material fact required to be stated therein or necessary to make the
     statements therein not misleading except insofar as such losses, claims,
     damages or liabilities are caused by any untrue statement or omission
     contained in information furnished in writing to the Company by such
     Warrant holder or such holder of common stock expressly for use therein,
     and each such holder by its acceptance hereof severally agrees that it will
     indemnify and hold harmless the Company and each of its officers who signs
     such registration statement and each of its directors and each person, if
     any, who controls the Company within the meaning of Section 15 of the
     Securities Act of 1933 with respect to losses, claims, damages or
     liabilities which are caused by any untrue statement or omission contained
     in information furnished in writing to the Company by such holder expressly
     for use therein.

9. APPLICABLE LAW. This Warrant shall be governed by, and construed in
accordance with, the laws of the State of Minnesota.

DATED:  December 28, 1998

                                        SPECTRASCIENCE, INC.



                                        ------------------------------
                                        Chester E. Sievert, Jr.
                                        President and CEO


THE SECURITIES EVIDENCED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES
ACT OF 1933 OR APPLICABLE STATE SECURITIES LAWS. THESE SECURITIES HAVE BEEN
ACQUIRED FOR INVESTMENT AND MAY NOT BE OFFERED FOR SALE, SOLD, PLEDGED, ASSIGNED
OR OTHERWISE DISPOSED OF, AND NO TRANSFER OF THE SECURITIES WILL BE MADE BY THE
COMPANY OR ITS TRANSFER AGENT, IN THE ABSENCE OF SUCH REGISTRATION OR AN OPINION
OF COUNSEL ACCEPTABLE TO THE COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED.


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                              AMENDMENT TO WARRANT

      This Amendment to Warrant ("Amendment"), dated December 21, 1999, amends
that certain warrant, No. PB122898-____ dated December 28, 1998, issued by
SPECTRASCIENCE, Inc. ("the Company") to _______________ (the "Holder") that
entitles the Holder to the right to purchase _______________ shares of common
stock, par value $0.25, of the Company ("Common Stock"), at an exercise price of
$6.00 per share, prior to midnight, Minneapolis, Minnesota time on December 28,
1999 (the "Warrant"), subject to all the provisions of the Warrant.

      WHEREAS, the Company deems it in the best interest of the Company to
modify the terms of the Warrants;

      NOW, THEREFORE, in consideration of the above, the Warrant is amended as
follows:

      *     The first sentence of the first paragraph of the Warrant shall read
            as follows:

            This is to certify that, for value received, ___________ (the
            "Holder") is entitled to purchase, subject to provisions of this
            Warrant, from SPECTRASCIENCE, Inc., a Minnesota corporation (the
            "Company"), at any time from and after the date hereof and prior to
            June 28, 2000, (the "Exercise Period"), fully paid non-assessable
            shares of the Common Stock, twenty-five cent par value, of the
            Company ("Common Stock"), exercisable at the purchase price per
            share of $6.00, subject to provisions of this Warrant.

      *     All other references to December 28, 1999 throughout the Warrant
            will be modified to read June 28, 2000.

      *     All other provisions of the Warrant remain unchanged.

      This Amendment must be attached to the front of the Warrant and becomes an
      integral part of the Warrant. The Warrant together with this Amendment
      must be submitted to the Company if and when it is exercised.

      IN WITNESS WHEREOF, this Amendment was executed the day and year first
above written.

         SPECTRASCIENCE, Inc.



         -----------------------------
         Chester E. Sievert, Jr.
         President