60 male Syrian hamsters were treated on one ear with 2.5% selenium disulfide in a surfactant base and on the other ear with the same surfactant base. After treatment 15 animals were investigated by 3H-thymidine autoradiography, 15 animals by the colcemid method and 15 animals by the in vivo double labelling technique with 3H- and 14C-thymidine. In 15 animals the porportion of labeled cells was determined which still had contact with the basal lamina in the sebaceous gland 6 days after 3H-thymidine injection. Besides an increase in sebaceous gland size and in cell proliferation, a shortening of the S phase and a reduction of the labeled sebaceous gland cells which still have contact with the basal lamina of the sebaceous gland 6 days after 3H – thymidine injection were determine