In the past, several authors described an association of cutaneous malignant melanoma (MM) with other neoplasms. As their results were not conclusive, we designed this study with the aim to determine whether the frequency and spectrum of coexisting neoplasms in patients with cutaneous MM are either a significant or a random event. Therefore, the histories of 623 patients with primary MM from our clinic have been evaluated by a direct questionnaire. Diagnosis of MM has been established by histologic examination after excisional biopsy. The male/female (M/F) ratio was 240/383, the mean age 52.5 years (range 14-93). The distribution of risk groups yielded 277 patients (M/F = 90/187) for low risk (Breslow < 0.75 mm trunk, < 1.50 mm extremities), 245 patients (M/F = 105/140) for intermediate risk (Breslow 0.76-3.00 and 1.51-5.00 mm, respectively). 101 patients (M/F = 45/56) for high risk (Breslow > 3.00 and > 5.00 mm, respectively). 64 patients (10.3%) had associated primary carcinomas including 7 patients with 2 primary carcinomas compared to a control group (n = 313) with 12 carcinomas (3.8%). 50% of the carcinomas were diagnosed before the diagnosis of melanoma. The M/F ratio of this group was 25/39, the mean age at diagnosis of MM 62.7 years (range 28-91), the mean age at diagnosis of carcinoma 55.6 years (range 29-90). In the female group, breast cancer predominated (18/39), followed by uterus (7/39) and basal cell carcinoma (7/39); in the male group, basal cell carcinoma (10/25) was followed by prostate cancer (6/25).(ABSTRACT TRUNCATED AT 250 WORDS)