The decisions of the EPO may only be based on grounds or evidence on which the parties concerned have had an opportunity to present their comments.

This provision is intended to ensure that no party can be taken by surprise by grounds for a decision against his application on which he did not have an opportunity to present his comments.

In substantive examination, the applicant must have an opportunity of presenting his comments on all the grounds invoked against his application.

In opposition proceedings, if the patent is to be revoked, it should be ensured that the proprietor of the patent in particular is given sufficient opportunity to defend himself and, similarly, if the oppositions are to be rejected or if, despite the claims of the opponents, the patent is to be maintained in amended form, the opponents in particular should be given the same opportunity.