Rules 28 and 28a of the European Patent Office have been amended with effect from October 1, 1996. Before amendment, the rules provided that for applications that described inventions requiring the use of microorganisms that were not otherwise available to the public, the requirement of sufficiency of disclosure could be met by reference to a deposit of the microorganisms in one of a number of specified culture collections. Although the deposit had to be made available to the public after publication of the patent application, the depositor could restrict access to the deposited samples to named experts up to the point the European Patent was granted or the application became abandoned or was withdrawn.

The revised rules replace reference to "microorganisms" by reference to "biological material" which means any material containing genetic information which is capable of self reproducing or of being reproduced in a biological system.

The second amendment effectively overrules some case law that had held that for the provisions of Rule 28 to apply, the patent applicant and the depositor of the microorganism in a culture collection had to be the same. Under revised Rule 28 this is no longer required although details of the depositor must be included in the patent application and the EPO must be provided with evidence that the depositor has authorized the patent applicant to refer to the deposit in the patent application.

The third amendment changes the rules relating to the public's access to deposits where the patent application is abandoned or withdrawn. The amendment permits the depositor to require that in such circumstances, access to the deposit can be confined to experts for up to twenty years from the date of filing of the patent application.