A morphometric study of cat sebaceous glands was performed to evaluate the effects of castration and testosterone treatments. Skin biopsies were taken in six cats before castration, after castration and after the testosterone injections administered after castration (total number of biopsies: 18). Ninety 8μm thick sections of each biopsy were assessed for image analysis processing (SAMBA 2005, ALCATEL TITN). The variations in glands and cells size were evaluated on digitized microscopic images by morphometric parameters included in the SAMBA software package. An original software was developed for the analysis of the spacial gland structure. The best morphometric parameters were selected in a first step of the study, and included the nuclear surface (NS), the cell surface (CS) and the nuclear/cellular surface ratio (N/C). These three parameters were then compared in each group of samples for the six cats. It was shown that after castration the N/C (21%) significantly increased compared with prior to castration (12±6%). This 59±8% increase was mainly due to cell cytoplasm shrinking reflecting a decrease of the cell activity. The testosterone administered after castration produced a reverse effect with a N/C ratio back to normal (11·4%) and a significant cell cytoplasm and gland enlargement as shown by the three dimension constructions. This morphometric data correlated with the measurement of sebum and Fel d I productions. The negative effects of castration and the positive effects of testosterone on the sebaceous cells and glands volume favour the hypothesis that cat sebaceous cells are subject to hormonal control this is also likely to apply to the Fel d I production.