<PAGE>   1
                     U.S. SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                                 FORM 10-KSB/A1

(Mark One)

[X]     ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
                              EXCHANGE ACT OF 1934
                  For the Fiscal Year Ended December 31, 1998

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

                         COMMISSION FILE NUMBER 0-20791

                           AMARILLO BIOSCIENCES, INC.
                 (NAME OF SMALL BUSINESS ISSUER IN ITS CHARTER)

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

  800 WEST 9TH AVENUE, AMARILLO, TEXAS                     79101
(Address of principal executive offices)                 (Zip Code)

         ISSUER'S TELEPHONE NUMBER, INCLUDING AREA CODE: (806) 376-1741


Securities registered under Section 12(b) of the Exchange Act:

                                      None.

Securities registered under Section 12(g) of the Exchange Act:

                          Common Stock, Par Value $.01
                                (Title of class)

         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
    ---     ---

         Check if there is no disclosure of delinquent filers in response to
Item 405 of Regulation S-B in this form, and no disclosure will be contained, to
the best of registrant's knowledge, in definitive proxy or information
statements incorporated by reference in Part III of this Form 10-KSB or any
amendment to this Form 10-KSB. [X]

         Revenues for its most recent fiscal year were $222,289

         As of March 9, 1999, there were outstanding 5,414,232 shares of the
registrant's common stock, par value $.01, which is the only class of common or
voting stock of the registrant. As of that date, the aggregate market value of
the shares of common stock held by nonaffiliates of the registrant (based on the
closing price for the common stock on the NASDAQ SmallCap Market) was
approximately $6,458,412.


<PAGE>   2

ITEM 10.          EXECUTIVE COMPENSATION.

         The following table sets forth for the three years ended December 31,
1998 compensation paid by the Company to its Chairman of the Board, President
and Chief Executive Officer, and to its former Executive Vice-President and
Chief Financial Officer. None of the Company's other executive officers had
annual salary and bonus in excess of $100,000 for services rendered during any
of the three years ended December 31, 1998.

                           SUMMARY COMPENSATION TABLE

<TABLE>
<CAPTION>
                                                                             Annual Compensation
                                                         ------------------------------------------------------------
  NAME AND PRINCIPAL POSITION                  YEAR           SALARY               BONUS         OTHER COMPENSATION
------------------------------------------     ----      -----------------       ------------    --------------------
<S>                                            <C>       <C>                     <C>            <C>
Dr. Joseph Cummins, Chairman                                                                                   --
     of the Board, President and                                                                 
     Chief Executive Officer..............     1998      $         150,000       $         --    $
                                               1997                120,000             20,000               12,000(3)
                                               1996                120,000                 --              252,000(4)
Charles Hughes, Executive Vice-                                                                                       
     President and Chief Financial                                                                                    
     Officer (1)..........................     1998                     --                 --                   --
                                               1997                147,435 (2)             --               10,333(3)
                                               1996                 75,000             10,000              157,575(5)
</TABLE>

(1)  Mr. Hughes terminated his employment with the Company on September 8, 1997.
(2)  Includes both 1997 salary and severance payments.
(3)  Represents a Company contribution to the Simplified Employee Pension Plan.
(4)  Represents the value of 30,000 shares of common stock issued at $5.00 per
     share and payment of withholding tax requirements in settlement of
     restricted stock grants and a Company contribution of $12,000 to the
     Simplified Employee Pension Plan.
(5)  Represents the value of 19,000 shares of common stock issued at $5.00 per
     share and payment of withholding tax requirements in settlement of
     restricted stock grants and a Company contribution of $7,500 to the
     Simplified Employee Pension Plan.




                                      2

<PAGE>   3

                              OPTION GRANTS IN 1998

        The following table sets forth certain information relating to options
granted in 1998 to the executive officers named above, to purchase shares of
common stock of the Company.

<TABLE>
<CAPTION>

                                               NUMBER OF                                                 
                                               SHARES OF                                                 
                                              COMMON STOCK          % OF TOTAL                                
                                               UNDERLYING        OPTIONS GRANTED     EXERCISE OR                             
                                                OPTIONS            TO EMPLOYEES       BASE PRICE    EXPIRATION
  NAME                                         GRANTED(#)            IN 1997            ($/SH)         DATE
-----------------------------------------     ------------       ---------------     -----------    ----------
<S>                                          <C>               <C>                  <C>           <C>    
John Smith...............................        40,000               67.8%           $1.75 (1)     09/13/2008
</TABLE>

(1) The fair market value of the common stock on the date of the grant.

                AGGREGATED OPTION EXERCISES AT DECEMBER 31, 1998
                           AND YEAR-END OPTION VALUES

        The following table sets forth information for the executive officers
named above, regarding the exercise of options during 1998 and unexercised
options held at the end of 1998.

<TABLE>
<CAPTION>

                                                                NUMBER OF SHARES OF        VALUE OF UNEXERCISED
                                                             COMMON STOCK UNDERLYING          IN-THE-MONEY
                                  SHARES                     UNEXERCISED OPTIONS AT            OPTIONS AT
                                 ACQUIRED ON     VALUE         DECEMBER 31, 1998(#)      DECEMBER 31, 1998($)(1)
NAME                             EXERCISE(#)   REALIZED($)  EXERCISABLE/UNEXERCISABLE   EXERCISABLE/UNEXERCISABLE
------------------------------- -------------  ------------ -------------------------   -------------------------
<S>                            <C>           <C>            <C>                         <C>
Joseph Cummins                       --             --         5,500    /     9,000        None    /     None
John Smith                           --             --            --    /    40,000        None    /     None
</TABLE>

(1)  Calculated based on the closing price of the common stock ($1.25) as
     reported by NASDAQ on December 30, 1998.

                   DIRECTOR COMPENSATION FOR LAST FISCAL YEAR

<TABLE>
<CAPTION>

                                                                         Cash Compensation                      Security Grants
                                                                  ------------------------------------          ---------------
                                                                                                                   NUMBER OF
                                                                                                                  SECURITIES
                                                                    MEETING                CONSULTING             UNDERLYING
                        NAME                                        FEES(1)                  FEES(2)                OPTIONS
-----------------------------------------------------             -----------             ------------          -------------
<S>                                                               <C>                     <C>                         <C>  
Stephen Chen, PhD                                                 $     2,000             $     45,950                5,000
James Cook                                                              2,000                    3,000                5,000
Thomas D'Alonzo                                                         2,000                        -                5,000
Katsuaki Hayashibara                                                    2,000                       --                5,000
Brian McLean, MD                                                        2,000                       --                5,000
Dennis Moore, DVM                                                       2,000                    4,500                5,000
James Page, MD                                                          1,000                    1,200                5,000
</TABLE>

(1)  Each director receives a fee of $1,000 for in-person attendance at each
     regular directors' meeting.

(2)  Each director receives $1,200 per day for employment on special projects or
     assignments.

                                      3

<PAGE>   4
ITEM 11. SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT.

     As of December 31, 1998, there were 5,414,232 shares of the Company's
common stock outstanding. The following table sets forth as of December 31,
1998, the beneficial ownership of each person who owns more than 5% of such
outstanding common stock:


<TABLE>
<CAPTION>
NAME AND ADDRESS                                  NUMBER OF SHARES   PERCENT OF TOTAL
-----------------------------------------------   ----------------   ----------------
<S>                                               <C>                <C> 
Hayashibara Biochemical Laboratories, Inc.                                   
2-3 Shimoishii 1-chome                                                       
Okayama 700, Japan                                     1,232,856            22.8

Dr. Joseph Cummins                                                           
800 West 9th Avenue                                                          
Amarillo, Texas 79101                                    676,814(1)         12.5

Mesa Operating Limited Partnership                                           
P.O. Box 2009                                                                
Amarillo, Texas 79189-2009                               315,120             5.8

Mochida Pharmaceutical Co., Ltd.                         
7, Yotsuya 1-chome
Shinjuku-Ku
Tokyo 160, Japan                                         300,000             5.5
</TABLE>

(1)  Includes an aggregate of 337,668 shares of common stock held by Joseph
     Cummins as trustee under certain trusts for the benefit of his children and
     10,590 shares owned by Dr. Cummins' wife.

     The following table sets forth the beneficial ownership of the Company's
stock as of December 31, 1998 by each director, and by all executive officers
and directors as a group:


<TABLE>
<CAPTION>
DIRECTORS                            NUMBER OF SHARES   PERCENT OF TOTAL
----------------------------------   ----------------   ----------------
<S>                                  <C>                <C> 
Joseph Cummins                           676,814(1)            12.5

Dennis Moore                             149,616                2.8

James Cook                                66,600(2)             1.2

Katsuaki Hayashibara                      48,240                1.0

Stephen Chen                               9,400                  *

Thomas D'Alonzo                            3,000                  *

Brian McLean                                  --                 --

James Page                                    --                 --

Total Group (all directors and           
executive officers - 8 persons)          953,670               17.6
</TABLE>

*    Less than 1%

(1)  Includes an aggregate of 337,668 shares of common stock held by Joseph
     Cummins as trustee under certain trusts for the benefit of his children and
     10,590 shares owned by Dr. Cummins' wife.

(2)  All of such shares are owned jointly with Mr. Cook's wife.


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<PAGE>   5



                                   SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the 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.


                             By: /s/ JOSEPH M. CUMMINS
                                -----------------------------------------------
                                Joseph M. Cummins, Chairman of the Board,
                                President, Chief Financial Officer and Chief
                                Executive Officer


Date: April 6, 1999        
      -------------

Pursuant to the requirements of the Securities Exchange Act of 1934, this report
has been signed below by the following persons on behalf of the registrant and
in the capacities and on the dates indicated.

<TABLE>
<CAPTION>

Signature                             Title                                         Date
---------                             -----                                         ----
<S>                          <C>                                        <C>
/s/ JOSEPH M. CUMMINS                                                         April 6, 1999
----------------------------  Chairman of the Board,                     ------------------------------
Joseph M. Cummins             President, Chief Financial
                              Officer, Director and
                              Chief Executive Officer

/s/ JAMES COOK                Director                                        April 6, 1999
----------------------------                                             ------------------------------
James Cook

/s/ DENNIS MOORE              Director                                        April 6, 1999
----------------------------                                             ------------------------------
Dennis Moore

/s/ JAMES PAGE                Director                                        April 6, 1999
----------------------------                                             ------------------------------
James Page

/s/ THOMAS D'ALONZO           Director                                        April 6, 1999
----------------------------                                             ------------------------------
Thomas D'Alonzo
</TABLE>