Basal cell carcinomas are can be induced by ionizing radiation, in particular in patients with the rare autosomal dominant basal cell nevus syndrome (BCNS). These patients also are prone to medulloblastomas, and curative ionizing radiation therapy for the latter is followed soon by the development of sheets of basal cell carcinomas in the overlying skin. Positional cloning of the gene mutant is BCNS patients has identified the hedgehog signaling pathway as crucial to the development of all basal cell carcinomas and presumably to this susceptibility to post‐ionizing radiation carcinogenesis. Thus this pathway is a candidate for susceptibility to second, post‐therapy cancers in the broader population. Med. Pediatr. Oncol. 36:555–558, 2001. © 2001 Wiley‐Liss, Inc.