Oral mucosal biopsies from 11 healthy volunteers, 7 women and 4 men, were analysed for the localization of androgen, oestrogen and progesterone receptors. The samples were dissected as quickly as possible and immediately frozen in liquid nitrogen to be stored at -70 degrees C. Only androgen receptors could be detected by the methods used. These were mainly located in the nuclei of basal epithelial cells, and to some extent in the nuclei of fibroblasts and endothelial cells. Failure in the localization of oestrogen and progesterone receptors might have been due either to low numbers of receptors or to the insensitivity of antibodies used. The method is thus suitable only for detecting androgen receptors.