Fatigue properties of shape-memory alloys (SMA) play an important role in actuator and certain biomedical applications. Since a small cyclic stress can trigger martensitic transformation when the mean stress is close to a critical stress, it is crucial to understand the effect of mean stress. This paper examines mean stress effects on fatigue properties of a NiTi SMA through systematic experiments. Preliminary results indicate that the cycles-to-failure has a non-monotone dependence on the mean strain at fixed strain amplitude. (C) 1999 Elsevier Science S.A. All rights reserved.