Basal cell carcinomas (BCCs) obtained from 22 subjects undergoing microscopically controlled surgery were transplanted to 40 athymic (nude) mice. With no further immunosuppression of the mice, no tumor growth was noted in the first 14 attempts. When mice were further immunosuppressed with anti‐lymphocyte serum (ALS) injections and by splenectomy, successful tumor growth was achieved in 15 of 22 mice by a subcutaneous implantation technique and in 1 of 4 by a superficial grafting technique. Transplanted BCC retained the morphology and basement membrane proteins typical of human BCC. As determined by autoradiography, ³H‐thymidine was incorporated primarily in the peripheral palisaded cells of the transplanted tumor. Successful use of the athymic mouse model for study of human BCC requires use of mice further immunosuppressed by splenectomy and ALS, and the use of a subcutaneous implantation technique. With the use of this model, studies of the biology of human BCC may be possible.