EXHIBIT 99.1 CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002 In connection with the annual report on Form 20-F of AltaRex Corp. (the "Company") for the period ended December 31, 2002 as filed with the Securities and Exchange Commission on the date hereof (the "Report"), the undersigned, Antoine A. Noujaim, Chief Executive Officer of the Company, hereby certifies, pursuant to 18 U.S.C. Section 1350, that: (1) the Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and (2) the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company. Dated: June 30, 2003 /s/ Dr. Antoine A. Noujaim --------------------------------- Dr. Antoine A. Noujaim Chief Executive Officer A signed original of this written statement required by Section 906, or other document authenticating, acknowledging, or otherwise adopting the signature that appears in typed form within the electronic version of this written statement required by Section 906, has been provided to AltaRex Corp. and will be retained by AltaRex Corp. and furnished to the Securities and Exchange Commission or its staff upon request.