This letter describes the results ofinsituobservations of dislocation behavior in In‐doped GaAs crystals at high temperatures using synchrotron radiation topography and high‐temperature stressing apparatus. The generation and propagation processes of dislocations in a preyield stage have been investigated by making a comparison with undoped crystals. We find that there is a one‐directional predominance in the generation and propagation of dislocations in In‐doped crystals.