Agricultural Patent Reform Act of 1984 - Amends the patent laws to extend the terms of patents which encompass specified products or methods for using a product, including methods of manufacturing which primarily use recombinant DNA technology, any of which are subject to certain nonpatent regulatory review periods. Sets forth the terms and conditions of such extension, including a five-year limitation on the extension and a 25-year maximum patent term for the earliest filing.

Directs the Commissioner of Patents to notify the appropriate Federal agency upon receipt from the product sponsor of a notice of extension to determine the applicable regulatory review period and whether, within that period, the sponsor acted with due diligence. Provides for notice and informal hearings for persons interested in such determinations. Permits the setting of fees to cover the costs of review.

Directs the Commissioner, upon a final determination of the applicable regulatory review period, to issue to the owner of record of a patent a certificate of extension stating the fact and length of the extension and identifying the product and the use and the claim to which such extension is applicable. Makes such certificate a part of the original patent.

Limits the application of such patent term extension to patents for: (1) any new animal drug or antibiotic subject to regulation under the Federal Food, Drug, and Cosmetic Act; (2) any veterinary biological product subject to regulation under the Virus-Serum-Toxin Act; (3) any pesticide subject to regulation under the Federal Insecticide, Fungicide, and Rodenticide Act; and (4) any chemical substance or mixture subject to regulation under the Toxic Substances Control Act.