The paper deals with the numerical investigation of time-dependent magnetic field influence on GaAs crystal growth by vertical Bridgman method. Fully unsteady numerical simulation is performed for three types of dynamic magnetic fields: rotating magnetic field (RMF), axial alternating magnetic field (AMF) and travelling magnetic field (TMF). The fields of stream function in the melt, temperature and dopant distribution in the melt and in the grown crystal with and without magnetic field are obtained and analyzed. RMF is found to pose significant influence on both azimuthal and meridional melt flows towards their intensification, and to substantially reduce the interface deflection. Higher magnetic field intensity results in the crystal-melt interface shape change from a concave interface to W-shaped one. At certain value of magnetic field intensity the steady-state flow regime becomes unstable and the transition to time-dependent regime is observed. The influence of AMF on GaAs crystal growth is found to be similar to that of static magnetic field. Application of travelling magnetic field significantly changes the flow structure, the interface shape and the dopant distribution in a melt and grown crystal. Depending on the propagation direction it can make either positive or negative effect on the resulting flow structure. (C) 2004 Elsevier B.V. All rights reserved.