The objective of this paper is to clarify the performance of a Wells air turbine using self-pitch-controlled blades under the real sea conditions and to obtain the useful information about the optimum setting angle. Experimental investigations were performed by model testing of a rotor with fixed blades under steady flow conditions. Then, the running and starting characteristics under sinusoidally oscillating flow conditions were obtained by a computer simulation using a quasi-steady analysis. As a result, the performances of the air turbine using self-pitch-controlled blades under the real sea conditions were clarified, and a suitable choice of design factor has been suggested for the setting angle of the rotor. © 2002 Éditions scientifiques et médicales Elsevier SAS. All rights reserved.