During a 1-yr period, a 50-yr-old man had developed 6 basal cell skin cancer lesions on his scalp and face, 5 of which were localized on the right side of his head. The man had used an analog cellular telephone during 1987-1992; after 1992, he used a digital cellular telephone. In addition, he had used a cordless telephone since 1997. He always placed a phone on his right ear during phone calls. The right side of this individual's head contained 5 of the 6 tumors that eventually developed.