In T 376/90 (OJ 1994, 906) the first question to be decided was whether the opposition was admissible, and whether it was correct for the preliminary decision on this point to be made appealable only together with the final decision. As to the latter point, the opposition division decided on the admissibility in an interlocutory decision within the meaning of Art. 106(2) EPC (former Art. 106(3) EPC 1973), i.e. a decision which did not terminate the proceedings as regards one of the parties. In the board's view, according to the clear language of that provision, such an interlocutory decision could only be appealed together with the final decision, unless the decision allowed separate appeal. Whether to allow a separate appeal was within the discretion of the opposition division. The board held that this discretion under Art. 106(2) EPC (former Art. 106(3) EPC 1973) was properly exercised by the opposition division with a view to enabling a decision on the substantive issues to be reached as soon as possible.
In G 9/92 (OJ 1994, 875), the Enlarged Board of Appeal set out the implications of an admissible appeal against an interlocutory decision of the opposition division where the sole appellant is, on the one hand, the patent proprietor and, on the other, the opponent. If the patent proprietor is the sole appellant against an interlocutory decision maintaining a patent in amended form, neither the board nor the non-appealing opponent as a party to the proceedings as of right may challenge the maintenance of the patent as amended in accordance with the interlocutory decision. If, however, the opponent is the sole appellant against such an interlocutory decision, the patent proprietor is primarily restricted to defending the patent in the form in which it was maintained by the opposition division in its interlocutory decision. The board may reject as inadmissible any amendments proposed by the patent proprietor as a party to the proceedings as of right if they are neither appropriate nor necessary.