A rate equation model is applied to analyze surface segregation in InGaAs and related compounds during the growth of these materials by molecular beam epitaxy (MBE). General trends in segregation are examined as a function of temperature, the V/III ratio and the type of substrate. It is suggested that the principal segregation mechanism is related to a near-equilibrium established between the volatile group III species on the growth surface and in the crystal bulk. In particular, this mechanism results in different manifestations of surface segregation for InGaAs and GaAlAs.