There are many forms of nonmelanoma skin cancer, although the term usually refers to the most common forms, basal and squamous cell carcinomas of the skin. The definitions of basal and squamous carcinomas depend on histopathologic features, and clinical diagnoses are often reliable. Various classification schemes have been proposed, including those based on clinical or histologic appearance, etiology, or prognosis. The public health burden of these tumors has not been fully defined and includes mortality, morbidity, social impact, and cost. Measures of morbidity include incidence and measures of impairment, disability, and handicap. Other issues involving etiology, management, prevention, and early detection remain to be investigated further.