Twenty-nine cases of basal cell carcinoma were studied with immunoperoxidase techniques for the detection of carcinoembryonic antigen. Results presented in the text would indicate that a high percentage of basal cell carcinomas have sweat gland histogenetic origins and that this is independent of its morphologic features. The use of immunohistochemical techniques in the detection of biological markers demonstrates once again their value not only in identifying a disease but also in determining its histogenetic origins.