Several recent studies have linked cigarette smoking to an increased risk of squamous cell skin cancer, but previous studies have found no correlation between smoking and basal cell carcinoma. This article is a retrospective chart review of 200 patients who had Mohs' surgery for basal cell carcinoma at the Mayo Clinic in Rochester, Minnesota, between 1986 and 1990. In patients with tumors less than or equal to 1.0 cm, 30% were smokers. In patients with tumors 1.1 to 2.0 cm, 42% were smokers. In patients with tumors 2.1 to 4.9 cm, 56% were smokers; and in patients with tumors greater than or equal to 5.0 cm, 50% were smokers. Cigarette smoking is associated with an increased prevalence of basal cell carcinomas larger than 1.0 cm in diameter.