Films of As2Se3and Sb2Se3and their mixtures have been studied by electron microscopy and diffraction. On heating amorphous As2Se3films no change occurs, but the Sb2Se3films and mixtures of Sb2Se3and As2Se3transform to give small single crystals. These crystals have theircaxes parallel to the substrate and give mainly (010) and (100) planes normal to the beam. Rate of nucleation is independent of temperature, indicating nucleation from predetermined nucleation centers. Growth rate increases with increasing temperature, but involves very little migration of material, implying that surface migration is very slow.