Concerning development of propulsive performances for high-speed-catamarans, the most significant influence can be given by reduction of the wetted surface area. For this purpose, concept of the air cushion catamaran has been proposed by the authors in 1976, however, augmentation of the wave resistance due to cushion pressure has been remained in obscurity. The intent of this paper is twofold. One of the purpose is to establish an experimental method for determination of the wave resistance due to cushion pressure. The other purpose is an evaluation of the resistance characteristics of air cushion catamarans. As a conclusion, it is shown that a remarkable power saving can be expected by developments of air cushion catamarans.