The objective of this paper is to predict the dislocation density in GaAs crystals grown from the melt using a crystallographic model. The effects of the temperature gradient field, the growth direction and the initial dislocation density on the dislocation multiplication in the crystal are investigated. The results show that a small increment in temperature gradient results in a large increment in dislocation density. Comparison of the calculated dislocation density for the GaAs crystal grown along the  and [111) directions shows that the growth direction has a significant effect on dislocation multiplication. Dislocation multiplication behaviour in the individual slip system is also investigated. The dislocation density in the slip system is strongly affected by the resolved shear stress in such a slip system, but only weakly affected by the initial dislocation density in the seed crystal.