The risk of developing subsequent nonmelanoma skin cancers. Data from the Southeast Arizona Skin Cancer Registry collected during 1985 through June 1988 were used in this study. Patients who had a nonmelanoma skin cancer (basal cell or squamous cell carcinoma) removed in 1985 were observed until subsequent nonmelanoma skin cancers developed or until June 30, 1988. Twelve categories of nonmelanoma skin cancers were developed on the basis of the type of first nonmelanoma skin cancer and type of second, third, and fourth nonmelanoma skin cancers. Analyses showed the highest risk of a subsequent nonmelanoma skin cancer developing was within 1 year (36.39%), the rate of developing another nonmelanoma skin cancer depended on type (squamous cell carcinoma, 100%; basal cell carcinoma, 44.23% to 83.65%), and total risk decreased during the 1277 days of the study. 