The mean velocities of α, β and screw dislocations in doped GaAs have been determined by X-ray topography. Although the velocities of β dislocations were found to be nearly equal to those measured in undoped material, the velocities of α and screw dislocations were lower. The activation energies for dislocation motion were found to be approximately the same as in undoped material, except for temperatures higher than 400°C and values of the resolved shear stress, σ, less than 10 MPa. In this range, the mobilities of α and screw dislocations were more severely reduced and were time-dependent. We suggest that these different effects are related to a selective interaction between the dopant (In) and α partials.