According to Art. 99 (3) EPC (former Art. 99 (4) EPC 1973), opponents shall be parties to the opposition proceedings as well as the patent proprietor. It is clear from this provision that multiple admissible oppositions do not initiate a corresponding number of parallel opposition proceedings but only a single one. Each opponent can rely on an opposition ground duly submitted by other opponents and communicated to all parties in accordance with R. 79 (2) EPC (former R. 57 (2) EPC 1973), both in the opposition proceedings and in any subsequent appeal proceedings (T 270/94, T 620/99, T 774/05).