Relative contributions of the solutal natural and Marangoni (thermal and solutal) convective flows to the melting process of a GaSb-InSb-GaSb system under normal and reduced gravity conditions were investigated. Numerical simulation results show that thermal Marangoni convection enhances the melting near the free surface under both normal and zero gravity conditions. The contribution of the solutal Marangoni convection to the flow field is less than that of the thermal Marangoni convection under normal gravity. This is due to the fact the heavier component sinks to the lower part of the melt, and the concentration gradient along the free surface becomes very gentle. Consequently, the intensity of the solutal Marangoni convection is very small in spite of the associated Marangoni number being large. On the other hand, the interface shape is greatly affected by the presence of solutal Marangoni convection under the reduced gravity field although the flow velocity of the solutal Marangoni convection is very small. (C) 2002 Elsevier Science B.V. All rights reserved.