This paper describes an experimental programme carried out in a laboratory channel, to investigate the velocity distributions over a rippled bed in combined wave-current flows. In this study, waves propagate against a turbulent current. Velocity measurements were made with a laser-Doppler anemometer. The Nikuradse roughness lengthks, of the bed has been estimated from the traditional logarithmic velocity profile for current alone. The most significant effect of the superposition of waves on a current is the increase of the apparent roughness of the bed with increasing wave height. This effect is well described by Sleath's [49] model. As for rough flat beds, the turbulence intensity over ripples varies inversely with height at sufficiently large distance from the bed for wave-dominated flows.