The generation and multiplication of dislocations in an indium phosphide (InP) single crystal grown by the vertical gradient freeze (VGF) process is predicted using a crystallographic model. This model couples microscopic dislocation motion and multiplication to macroscopic plastic deformation during the crystal growth process. During growth of an InP crystal, dislocations are generated in the plastically deformed crystal as a result of crystallographic glide caused by excessive thermal stresses. The temperature fields are determined by solving the partial differential equation of heat conduction in a VGF crystal growth system. The effects of growth direction and growth parameters (i.e. imposed temperature gradients, crystal radius and growth rate) on dislocation generation and multiplication in an InP crystal are investigated. Dislocation density patterns on the cross section of an InP crystal are numerically calculated and compared with experimental observations. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.