A B S T R A C TNumerical simulations of the evolution of strange-mode instabilities into the non-linear regime have been performed for massive objects and Wolf-Rayet stars. Velocity amplitudes above 10 2 km s ¹1 can be reached which exceed the escape velocity and imply mass loss for massive objects. Although for Wolf-Rayet stars direct mass loss is not observed, the velocity field established by the instability may be sufficient to initiate a line-driven wind. The results are sensitive to the numerical treatment of the problem.