Kinetic effects limiting the growth rate in MOVPE of III-V compounds are analyzed. A general mechanism-the blocking of group III species adsorption sites by methyl radicals-is suggested and accounted for in an original model of surface chemistry. using experimental data on the decomposition of group III metal-organic precursors on III-V semiconductor surfaces. The application of the model to GaAs. GaN and InP MOVPE provides a good agreement between the predicted and measured growth rates in a wide range of growth conditions and reactor types.