<PAGE>   1
                                  United States
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


                                   FORM 10-QSB


[X]       QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
          EXCHANGE ACT OF 1934


For the quarterly period ended           MARCH 31, 2000
                               ------------------------------------


[ ]       TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
          EXCHANGE ACT OF 1934

                         Commission File Number 0-20791


                           AMARILLO BIOSCIENCES, INC.
--------------------------------------------------------------------------------
        (Exact name of small business issuer as specified in its charter)

             TEXAS                                               75-1974352
--------------------------------------------------------------------------------
(State or other jurisdiction of                                (IRS Employer
 incorporation or organization)                              Identification No.)

      800 West Ninth, Amarillo, TX                                 79101
--------------------------------------------------------------------------------
(Address of principal executive offices)                         (Zip Code)

              806-376-1741                                    FAX 806-376-9301
--------------------------------------------------------------------------------
(Issuer's telephone number, including area code)


     Check whether the issuer (1) filed all reports required to be filed by
Section 13 or 15(d) of the Exchange Act during the past 12 months (or for such
shorter period that the registrant was required to file such reports), and (2)
has been subject to such filing requirements for the past 90 days.
Yes X . No    .
   ---    ---

As of March 31, 2000 there were 7,472,157 shares of the issuer's common stock
outstanding.

                         This report contains 12 pages.


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<PAGE>   2


                           AMARILLO BIOSCIENCES, INC.


                                      INDEX


<TABLE>
<CAPTION>
PART I:        FINANCIAL INFORMATION                                            PAGE NO.
                                                                                --------
<S>            <C>                                                              <C>
Item 1.        Financial Statements
               Consolidated Balance Sheets - December 31, 1999 and March
               31, 2000 ................................................                3

               Consolidated Statements of Operations - Three Months
               Ended March 31, 1999 and 2000 and Cumulative from June
               25, 1984 (Inception) through March 31, 2000 .............                4

               Condensed Consolidated Statements of Cash Flows - Three
               Months Ended March 31, 1999 and 2000 and Cumulative
               from June 25, 1984 (Inception) through March 31, 2000 ...                5

               Notes to Consolidated Financial Statements ..............                6

Item 2.        Management's Plan of Operations .........................                8

PART II:       OTHER INFORMATION


Item 2.        Changes in Securities and Use of Proceeds ...............               10

Item 5.        Other Information .......................................               10

Item 6.        Exhibits and Reports on Form 8-K ........................               11

Signatures .............................................................               12
</TABLE>


                                       2
<PAGE>   3


                   AMARILLO BIOSCIENCES, INC. AND SUBSIDIARIES
                      (COMPANIES IN THE DEVELOPMENT STAGE)

                           CONSOLIDATED BALANCE SHEETS

<TABLE>
<CAPTION>
                                                                  DECEMBER 31,        MARCH 31,
                                                                      1999              2000
                                                                  ------------      ------------
<S>                                                               <C>               <C>
ASSETS
Current assets:
  Cash and cash equivalents                                       $  1,302,343      $  1,065,183
  Inventory                                                             48,639            48,639
  Other current assets                                                  32,137            35,672
                                                                  ------------      ------------
Total current assets                                                 1,383,119         1,149,494
Property and equipment, net                                            105,799           102,675
Patents, net of accumulated amortization of $89,806 and                 73,495            71,667
$91,634 at December 31, 1999 and March 31, 2000, respectively
                                                                  ------------      ------------
Total assets                                                      $  1,562,413      $  1,323,836
                                                                  ============      ============
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities:
  Accounts payable                                                $    521,199      $    510,331
  Accrued interest expense                                               3,526            18,542
  Other accrued expenses                                                82,198            18,927
                                                                  ------------      ------------
Total current liabilities                                              609,923           547,800
Notes payable to related party                                       1,000,000         2,000,000
                                                                  ------------      ------------
Total liabilities                                                    1,609,923         2,547,800
STOCKHOLDERS' EQUITY (DEFICIT):
  Preferred stock, $.01 par value:
     Authorized shares - 10,000,000
     Issued shares - none                                                   --                --
  Common stock, $.01 par value:
     Authorized shares - 20,000,000
     Issued shares - 7,472,157                                          74,722            74,722
  Additional paid-in capital                                        17,374,570        17,439,316
  Deficit accumulated during the development stage                 (17,496,802)      (18,738,002)
                                                                  ------------      ------------
Total stockholders' equity                                             (47,510)       (1,223,964)
                                                                  ------------      ------------
Total liabilities and stockholders' equity                        $  1,562,413      $  1,323,836
                                                                  ============      ============
</TABLE>


                            See accompanying notes.


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<PAGE>   4


                   AMARILLO BIOSCIENCES, INC. AND SUBSIDIARIES
                      (COMPANIES IN THE DEVELOPMENT STAGE)

                      CONSOLIDATED STATEMENTS OF OPERATIONS


<TABLE>
<CAPTION>
                                             Three months ended           Cumulative from
                                                  March 31,                June 25, 1984
                                        ------------------------------  (Inception) through
                                            1999              2000         March 31, 2000
                                        ------------      ------------  -------------------
<S>                                     <C>               <C>               <C>
Revenues:                               $         --      $         --      $  9,000,000
  Contract revenues
  Interferon sales                                --                --           420,974
  Interest income                             48,687            12,296         1,538,301
  Sublicense fees                                 --                --           113,334
  Royalty income                                  --                --            31,544
  Gain on ISI stock                               --             5,209           113,446
  Other                                           --               100           606,931
                                        ------------      ------------      ------------
                                              48,687            17,605        11,824,530

Expenses:                                  1,681,044           942,151        17,026,960
  Research and development
    expenses
  Selling, general, and                      324,329           301,638        12,630,430
    administrative expenses
  Interest expense                            28,849            15,016           870,142
                                        ------------      ------------      ------------
                                           2,034,222         1,258,805        30,527,532
                                        ------------      ------------      ------------

Loss before income taxes                  (1,985,535)       (1,241,200)      (18,703,002)
Income tax expense                                --                --            35,000
                                        ------------      ------------      ------------
Net loss                                $ (1,985,535)     $ (1,241,200)     $(18,738,002)
                                        ============      ============      ============
Basic and diluted loss per share        $      (0.37)     $      (0.17)
                                        ============      ============
Weighted average shares outstanding        5,414,232         7,472,157
                                        ============      ============
</TABLE>


                             See accompanying notes.


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<PAGE>   5


                   AMARILLO BIOSCIENCES, INC. AND SUBSIDIARIES
                      (COMPANIES IN THE DEVELOPMENT STAGE)

                 CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

<TABLE>
<CAPTION>
                                                     Three months ended         Cumulative from
                                                         March 31,               June 25, 1984
                                              ------------------------------  (Inception) through
                                                  1999              2000         March 31, 2000
                                              ------------      ------------  -------------------
<S>                                           <C>               <C>           <C>
Net cash used in operating activities         $   (914,627)     $ (1,242,369)     $(17,085,771)
                                              ------------      ------------      ------------

Net cash provided by (used in) investing
  activities                                        (6,130)            5,209          (569,077)
                                              ------------      ------------      ------------
Net cash provided by financing activities               --         1,000,000        18,720,031
                                              ------------      ------------      ------------
Net increase (decrease) in cash and cash
 equivalents                                      (920,757)         (237,160)        1,065,183
                                              ------------      ------------      ------------
Cash and cash equivalents at beginning
 of period                                       4,776,328         1,302,343                --
                                              ------------      ------------      ------------
Cash and cash equivalents at end of
 period                                       $  3,855,571      $  1,065,183      $  1,065,183
                                              ============      ============      ============
Supplemental Disclosure of Cash Flow
  Information

Cash paid for income taxes                    $         --      $         --      $     37,084
                                              ============      ============      ============

Cash paid for interest                        $         --      $         --      $      6,466
                                              ============      ============      ============
</TABLE>


                             See accompanying notes.


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<PAGE>   6


                   AMARILLO BIOSCIENCES, INC. AND SUBSIDIARIES
                      (COMPANIES IN THE DEVELOPMENT STAGE)

                   NOTES TO CONSOLIDATED FINANCIAL STATEMENTS


1.   Basis of Presentation. The accompanying consolidated financial statements,
     which should be read in conjunction with the consolidated financial
     statements and footnotes included in the Company's Form 10-KSB for the year
     ended December 31, 1999 filed with the Securities and Exchange Commission,
     are unaudited (except for the December 31, 1999 consolidated balance sheet
     which was derived from the Company's audited financial statements), but
     have been prepared in accordance with generally accepted accounting
     principles for interim financial information. Accordingly, they do not
     include all of the information and footnotes required by generally accepted
     accounting principles for complete financial statements. In the opinion of
     management, all adjustments (consisting only of normal recurring
     adjustments) considered necessary for a fair presentation have been
     included.

     Operating results for the three months ended March 31, 2000 are not
     necessarily indicative of the results that may be expected for the full
     year ending December 31, 2000.

2.   Loss per share. Loss per share is computed based on the weighted average
     number of common shares outstanding.

3.   On September 30, 1999 the Company entered into an Agreement to Convert Debt
     ("Agreement") with Hayashibara Biochemical Laboratories, Inc., a Japanese
     corporation ("HBL"). On October 15, 1999 pursuant to this Agreement, the
     Company issued 1,111,831 shares of its common stock to HBL in exchange for
     the release of $1,005,486.30 in debt and accrued interest.

     The Agreement called for an exchange to take place on November 30, 1999 in
     which HBL would contribute $1,000,000 to the Company and receive an
     equivalent amount of the Company's common stock. By mutual consent, the
     Company and HBL agreed that the November 30, 1000 transaction called for
     under the Agreement would not take place. Instead, HBL loaned $1,000,000 to
     the Company at an interest rate of 4 1/2%, compounded annually, payable on
     or before November 30, 2004 or one (1) year after FDA approval of a drug
     containing HBL interferon alpha for oral administration to humans,
     whichever occurs first.

     The Agreement also called for an exchange to take place on February 29,
     2000 in which HBL would contribute $1,000,000 to the Company and receive an
     equivalent amount of the Company's common stock. By mutual consent, the
     Company and HBL agreed that the February 29, 2000 transaction called for
     under the Agreement would not take place. Instead, on February 29, 2000,
     HBL loaned $1,000,000 to the Company at an interest rate of 4 1/2%,
     compounded annually, payable on or before February 29, 2005, or one (1)
     year after FDA approval of a drug containing HBL interferon alpha for oral
     administration to


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<PAGE>   7


     humans, whichever occurs first. This transaction discharged all remaining
     obligations of ABI and HBL under the Agreement.

4.   On December 29, 1999 405,932 options were granted to employees of the
     Company, including 300,000 granted to Joseph Cummins, President and CEO.
     Such options are exercisable at a price of $.875 per share, being the fair
     market value of the Company's stock on December 29, 1999, the date of
     grant. All of such options granted to employees were granted in
     consideration of the employees' agreement to relinquish salary during 2000,
     on the basis of two options granted for every $1.00 of salary voluntarily
     relinquished, with the amount of such relinquished salary being reflected
     in the Option Agreement signed with each employee, such options to vest
     monthly beginning in January, 2000, and to expire December 29, 2004.

     The Company recorded compensation expense in the amount of $64,746 during
     the first quarter in regard to these options. This amount represents the
     difference between the exercise price and the fair market value of the
     stock on the date of the salary reduction commitment by each of the
     employees, amortized over the 12 month vesting period.


                                       7
<PAGE>   8


ITEM 2. MANAGEMENT'S PLAN OF OPERATIONS

Amarillo Biosciences, Inc. is a development stage company, which is conducting
research and development activities focused on biologics for the treatment of
human and animal diseases. The Company has not commenced any significant product
commercialization and, until such time as it does, will not generate significant
product revenues. The Company's accumulated deficit has continued to grow, from
$17,496,802 at December 31, 1999 to $18,738,002 at March 31, 2000. Operating
losses are expected to continue for the foreseeable future and until such time
as the Company is able to attain sales levels sufficient to support its
operations.

During the next twelve months the Company will continue its research and
development activities, as well as the activities necessary to develop
commercial partnerships and licenses. The Company's expenditure of financial
resources during this period will fall principally into five broad categories,
as follows: Research and Development; Personnel; Consulting and Professional
(other than legal and accounting); Legal and Accounting; and Liquidity Needs.
The Company's expectations and goals with respect to these categories are
addressed separately below, by category:

RESEARCH AND DEVELOPMENT: Until it achieves commercial product sales, the
Company's business is research and development, and this is the area where the
Company's principal efforts will be expended during the next 12 months. The
Company has budgeted approximately $2.5 million for expenditure during the next
twelve months on research and development, inclusive of amounts to be expended
on the Company's Phase III Sjogren's syndrome clinical trials.

PERSONNEL: In addition to its intellectual property, the Company's principal
assets are its personnel. The Company has been successful in controlling its
personnel costs, both by maintaining its principal location in Amarillo, Texas,
and by ensuring maximum efficiency and utilization of existing personnel. The
Company has budgeted approximately $767,000 for personnel expenses during the
next twelve months, including salaries, payroll taxes, directors' and officers'
general liability insurance, and group life, health, and liability insurance.

CONSULTING AND PROFESSIONAL (EXCEPT LEGAL AND ACCOUNTING): The Company has
budgeted approximately $120,000 for expenditure on professional consultants in
the next 12 months. Consulting fees are expected to be paid to the Company's
scientific advisory board; to certain directors who perform specific consulting
tasks at the Company's request; and to a number of independent consultants, in
connection with the operation of the Company. The Company will continue to use
the services of consultants to complement the Company's small full-time staff,
where such is a more efficient utilization of the Company's resources.

LEGAL AND ACCOUNTING: Although the Company is not involved in litigation, it has
budgeted legal expenses of approximately $135,000 during the next 12 months.
Almost 20% of the Company's legal expenditures will be for preparation and
filing of patents and for maintenance of existing patents in a number of
countries. Other legal expenses will be related to compliance with laws and
regulations affecting public companies, licensing and contracting, and general
corporate matters. The Company does not presently have an in-house legal staff,
nor does it intend to put such a staff


                                       8
<PAGE>   9


in place during the next 12 months. The Company expects to continue Ernst &
Young as its auditors.

PUBLIC RELATIONS, INVESTOR RELATIONS AND SHAREHOLDER RELATIONS: The Company has
budgeted approximately $30,000 for public relations, investor relations and
shareholder relations during the next 12 months. The Company has also budgeted
sufficient amounts to maintain its comprehensive web site (www.amarbio.com).

LIQUIDITY NEEDS: The principal budget items discussed above, along with other
miscellaneous costs and expenses, will cause the Company to expend approximately
$4.1 million during the next twelve months including the substantial expense of
the Company's Phase III Sjogren's syndrome clinical trials. At March 31, 2000
the Company had available cash of $1,065,182. Proceeds from a private placement
which closed in April will generate cash in the amount of $790,000.

The Company will need to raise additional funds to complete the Sjogren's
syndrome clinical trials. If the Company is not successful in raising additional
funds, it will need to significantly curtail clinical trial expenditures and to
reduce staff and administrative expenses and may be forced to cease operations.


                                       9
<PAGE>   10


                           PART II - OTHER INFORMATION


ITEM 2. CHANGES IN SECURITIES AND USE OF PROCEEDS.

The Company's common stock was delisted from the Nasdaq SmallCap Stock Market on
October 12, 1999 because the Company did not have sufficient net tangible assets
to meet the applicable Nasdaq maintenance criteria. The Company has appealed
this decision to the Nasdaq Listing and Hearing Review Council. The Company's
common stock is currently traded on the Over the Counter Bulletin Board.

On April 15, 2000 the Company completed a private placement. The Company sold
316,000 unregistered shares of its voting common stock at a price of $2.50 per
share, generating $790,000 in cash. In addition, the investment package included
five year warrants allowing each investor the right to purchase 20% more stock,
or a total of 63,200 more shares than originally subscribed at a 25% increase in
price per share, and an additional 20% more stock, or a total of 63,200 more
shares than that originally subscribed at a 50% increase in price per share.


ITEM 5. OTHER INFORMATION

SUBSEQUENT EVENTS: On April 7, 2000 the Company announced the results from the
first of its double-blinded, placebo-controlled Phase III studies in primary
Sjogren's syndrome. These results demonstrated an improvement in unstimulated
whole saliva (UWS) production in those patients receiving the 150 International
Units of interferon alpha (IFN"). This increase correlated strongly with
subjective improvements in oral dryness, throat dryness and nasal dryness, as
determined by visual analog scale. Measurements of whole saliva and subjective
oral dryness had been designated the primary end points of the study. When an
intent-to-treat analysis was used to analyze these data, the results were not
significant. Because of the importance of UWS measurement, the Company plans to
focus on this measure in its second, ongoing Phase III study. The Company
intends to revise the primary end point of the study to be the change in UWS,
but will continue to measure all end points.


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<PAGE>   11


ITEM 6. EXHIBITS AND REPORTS ON FORM 8-K.

     EXHIBIT 27. Financial Data Schedule

     A report on Form 8-K, dated February 11, 2000 relating to the Agreement to
     Convert Debt between Amarillo Biosciences, Inc. and Hayashibara Biochemical
     Laboratories, Inc., was filed on February 16, 2000 reporting that the
     February 29, 2000 conversion of debt to stock would not take place, but
     instead that Hayashibara Biochemical Laboratories, Inc. would advance
     $1,000,000 as a loan to the Company.


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                                   SIGNATURES


     Pursuant to the requirements of Securities Exchange Act of 1934, the
Registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.



                                         AMARILLO BIOSCIENCES, INC.


Date: May 11, 2000
                                   By: /s/ JOSEPH M. CUMMINS
                                      ------------------------------------------
                                             Joseph M. Cummins
                                             President, Chief Executive Officer
                                             and Chief Financial Officer



                                       12
<PAGE>   13


                                 EXHIBIT INDEX


<TABLE>
<CAPTION>
EXHIBIT
NUMBER              DESCRIPTION
------              -----------
<S>                 <C>
  27                Financial Data Schedule
</TABLE>