The alarming increase in the incidence of cutaneous malignant melanoma in the United States emphasizes the importance of its early detection and treatment. Early detection requires accurate clinical recognition of both malignant and precancerous skin lesions (dysplastic nevi). This study presents data on dermatologists' and nondermatologists' ability to diagnose skin lesions. A total of 105 nondermatologist physicians, from first-year residents to practicing physicians, and forty-eight dermatologists were asked to identify color slides or photographs of eleven cutaneous lesions, including malignant melanomas, dysplastic nevi, and innocuous lesions such as seborrheic keratoses and common moles. Diagnosis of cutaneous lesions was generally inaccurate among nondermatologists. Only 38% correctly identified four or more of the six melanomas as melanoma of any type, and 58% were unable to diagnose dysplastic nevi. Only 17% categorized their relevant training as excellent or good. Improved training in the diagnosis of skin lesions for practicing physicians and house staff is required if mortality from malignant melanoma is to be decreased in the United States.