Numerical simulations of the Stokes boundary layer over a three‐dimensional wavy wall are performed in order to investigate the role played by infinitesimal wall imperfections in triggering transition to turbulence. Our results show flow patterns qualitatively similar to those experimentally detected. In particular the laminar, disturbed‐laminar and intermittent turbulent regimes are recovered. The characteristics of the above flow regimes are analyzed. ©1996 American Institute of Physics.