The specimen temperature rise during the ion milling of transmission electron microscopy (TEM) specimens of II-VI semiconductors has been measured systematically. The rise was found to increase with increasing ion energy, beam current and angle between the beam and the specimen surface. The growth of dislocation loops in CdTe and ZnTe during Ar+-ion beam thinning is considered to be due to thermally enhanced diffusion. A model involving competition between loop expansion and ion-beam etching is proposed, which leads to the possibility of preparing TEM specimens of CdTe and ZnTe free from visible radiation defects.