The anisotropy in the carrier mobility due to the presence of dislocations in III‐V compounds is determined using a method based on the equivalence of scattering energy loss and Joule heat created in the crystal. It is found that the mobility is a maximum perpendicular to the slip planes of 60° and 90° dislocations of both the &agr; and &bgr; types of dislocations. Screw dislocations do not cause any scattering and consequently do not affect the mobility through this mechanism.