Basal cell carcinoma (BCC) of the perianal and genital regions is very rare. In the period January 1985-September 1996, 106 BCCs were diagnosed at this institution, of which 84 (0.2%) were from the perianal (20) or genital (64) regions. Five perianal and 28 genital BCCs were from 2 patients with Basal Cell Nevus Syndrome and these were excluded. Thus 47 patients (20 male, 27 female) with 15 perianal BCCs and 36 genital BCCs were studied. The average age was 73 years (R: 45-100). Nine perianal BCCs occurred in men, 6 in women. Ten BCCs occurred in the pubic area (6 in men, 4 in women), 18 on the vulva, 6 on the scrotum and 2 on the penis. Three patients had 2 tumor sites. The average size of BCC was 1.95 cm (R: 0.5-5.2), 15 (29.4%) were ulcerated. Seventeen patients (36%) had a history of skin cancer on sun-exposed sites. Four patients (8.5%) had a history of prior radiotherapy to the pelvic region. Two patients had a history of chronic vulvar pruritis. One patient had Hailey Hailey disease affecting the perineum, one had acanthosis nigricans, one had prior methotrexate therapy and one had prior prednisone therapy. Treatments included wide excision (37), electrodesiccation and curettage (10), Mohs micrographic surgery (8) and CO 2 laser (1). Of 30 patients with ≥5 years follow up, 1 recurrence occurred 7 years following wide excision. There were no metastases. Depressed immune surveillance from UV radiation at distant sites and advancing age with local trauma may be important in the pathogenesis of BCCs of the perianal and genital regions.