A Norwegian melanoma project was carried out in 1989-1993 as a joint study by the dermatological, surgical, oncological, and pathological departments at the five university hospitals in Norway, Of 4,582 patients (2,894 women, 1,688 men) diagnosed and treated at the Department of Dermatology, Ullevål Hospital, 1,347 patients (833 women, 514 men) were included in the analysis, which consisted of a clinical evaluation and pathological investigation of their excised pigmented lesions. In all, 66 malignant melanomas were diagnosed, including 50 superficial spreading melanomas, seven lentigo maligna melanomas, eight nodular melanomas, and one acral lentiginous melanoma. Persons with red hair and skin type I/II were at increased risk of developing malignant melanoma. Superficial spreading melanomas excised during the study period had a significant lower histological thickness compared with those lesions excised before the study period.