The right to an oral hearing is an extremely important procedural right which the EPO should take all reasonable steps to safeguard (T 668/89; T 808/94; T 556/95, OJ 1997, 205; T 996/09; T 740/15). If a request for oral proceedings (see in this chapter III.C.4.) has been made, such proceedings have to be appointed. This provision is mandatory and leaves no room for discretion (T 283/88, T 795/91, T 556/95, T 1048/00, T 740/15), i.e. parties have an absolute right to oral proceedings (T 552/06, T 189/06, T 263/07, T 1426/07, T 653/08, T 1251/08, T 1829/10). Considerations such as the speedy conduct of the proceedings, equity or procedural economy cannot take precedence over this right (T 598/88, T 731/93, T 777/06). The right to be heard in oral proceedings subsists so long as proceedings are pending before the EPO (T 556/95, T 114/09).

The board in T 831/17 referred the following points of law to the Enlarged Board: 1. In appeal proceedings, is the right to oral proceedings under Art. 116 EPC limited if the appeal is manifestly inadmissible? 2. If the answer to the first question is yes, is an appeal against the grant of a patent filed by a third party within the meaning of Art. 115 EPC, relying on the argument that there is no alternative legal remedy under the EPC against the examining division's decision to disregard its observations concerning an alleged infringement of Art. 84 EPC, such a case of an appeal which is manifestly inadmissible?" The board's referral, which included an additional, third question (see in this chapter III.C.6.5. "Location of oral proceedings"), is now pending as G 2/19.

Where several parties are involved, e.g. in opposition proceedings, the EPC provides only for oral proceedings to which all the parties are invited, so as to respect the principles of judicial impartiality and the equal rights of parties (T 693/95).