In a study of the value of long-term follow-up after treatment of basal cell carcinoma, new skin cancers were found in 20% of patients examined during a one-year period. The majority of these new skin cancers were unsuspected by the patient. The risk of developing a new skin cancer was directly related to the number of previous basal cell carcinomas. While 20% of the entire group developed new skin cancers, 41% of those who had two or more previous skin cancers developed a new lesion, and of those having had three or more previous carcinomas, 56% developed skin cancers. The author believes that long-term follow-up for skin cancer patients is indicated to detect new tumors, and urges that all patients having had two or more previous basal cell carcinomas be followed up indefinitely.