In 280 melanoma patients all data concerning familial and personal history, histology, and therapy were verified. All patients underwent total-body skin examination to check for the presence of dysplastic nevus syndrome (DNS). In 257/280 patients (91.8%) solitary melanomas were found, while in 23/280 patients (8.2%) multiple melanomas occurring simultaneously or consecutively were ascertained. Surprisingly, among the 12/280 patients (4.2%) with familial variants of melanoma, multiple melanomas were not found in a increased frequency. In patients with DNS (regardless of whether sporadic or familial) the frequency of multiple melanomas is higher: in patients with solitary melanomas DNS was found in 27/257 (10.5%), while in patients with multiple melanomas DNS was diagnosed in 11/23 (47.8%) (P less than 0.0005). In both groups (solitary and multiple melanomas) the mean age of patients with DNS was around 10 years lower. The frequency of additional primary malignancies in patients with cutaneous melanomas was 8.6%, and did not vary according as whether patients had solitary or multiple melanomas with or without DNS.