EXHIBIT 5.1

                                 ATER WYNNE LLP
                                   LETTERHEAD

                               September 14, 2000

Board of Directors AVI BioPharma, Inc.
One S.W. Columbia Street, Suite 1105
Portland, OR  97258

Gentlemen:

     In connection with the registration of 1,725,120 shares of common stock,
$.0001 par value (the "Common Stock"), of AVI BioPharma, Inc., an Oregon
corporation (the "Company"), under the Registration Statement on Form S-3 to be
filed with the Securities and Exchange Commission on September 14, 2000, and the
proposed offer and sale of the Common Stock pursuant to the Registration
Statement, we have examined such corporate records, certificates of public
officials and officers of the Company and other documents as we have considered
necessary or proper for the purpose of this opinion.

     Based on the foregoing and having regard to legal issues which we deem
relevant, it is our opinion that the shares of Common Stock are validly issued,
fully paid and nonassessable.

     We hereby consent to the filing of this opinion as an exhibit to the
above-mentioned registration statement.

                                 Very truly yours,

                                 /s/ ATER WYNNE LLP

                                 ATER WYNNE LLP