Anisotropic effect of the hole drift velocity in silicon and germanium has been investigated with the time of flight technique by applying the electric field parallel to the <100 and <111 crystallographic axis. The measurements were performed for electric fields ranging from 10 to 3 × 104V/cm and temperatures from 40 to 200°K. The results indicate that the anisotropic effect vd<100/vd<111 increases with decreasing temperature and increasing electric field, and reaches a saturation value at high electric fields (⩽ 104V/cm). The maximum anisotropic effect for Ge is 1.25 at 40°K and for Si is 1.2 at 45°K. A qualitative analysis of the experimental data indicates that the anisotropic effect is due to the warped heavy-valence-band shape.