A case-control study of 232 cases of cutaneous malignant melanoma and 232 matched controls was performed to assess the association of the disease with nonmelanotic skin tumors--basal cell carcinomas, squamous cell carcinomas, and solar keratoses. There was a fourfold increase in risk of melanoma of all types when actinic tumors were present on the face. The risk was not restricted to the lentigo malignant melanoma class as might be expected but was significantly raised for superficial spreading melanoma and nodular melanoma as well (relative risk, 2.8; 95% confidence interval, 1.1-7.2). This relationship with lesions known to be associated with high-dose solar UV irradiation was supported by quantitative evidence that heavy sun exposure was associated with an increased risk of malignant melanoma.