The kinetics of growth of InSb thin films by In1 and Sb4 molecular beams on Si(100) surfaces has been studied. When an Sb4 beam is incident on the surface, Sb4 molecules are non-dissociatively chemisorbed below 820 K. In the temperature range 640-820 K there exist saturation adlayers with a saturation coverage of about 1 monolayer on the Si(100) surface and no antimony film growth can be observed. Below 640 K, nucleation and growth occur following the adsorption of Sb4 molecules. When In1 and Sb4 beams are incident simultaneously on the surface, below 880 K a dissociation reaction occurs on the surface whereas above 880 K Sb4 molecules are desorbed from the surface without reacting with indium adatoms. In the temperature range 700-800 K, however, the dissociation reaction of Sb4 into Sb2 proceeds with an increase in indium adatom population and InSb films are formed. Below 700 K, both impinging Sb4 molecules and dissociated Sb2 molecules stick to the surface, depending on the temperature. © 1986.