In 104 malignant melanoma patients who underwent lymphadenectomy (67 females, 37 males), correlations were studied between histologically diagnosed lymph node metastasis, the type of malignant melanoma and the depth of invasion according to Clark, as well as other parameters. In 35.6% of the patients, metastases of the primary tumor were found in one or several regional lymph nodes. In about one third of the patients, the clinical and histological lymph node findings were proven to diverge. The female:male ratio of generally about 2:1 shifted to 1:1 in the group of patients with lymph node metastasis, i.e. cases with lymph node metastasis were found significantly increased in the male sex, and also, when primary tumors were localized on the trunk. A prognostic correlation between the two parameters, sex and localization, is suggested by the high incidence of histologicallly diagnosed metastases in 1 or 2 lymph node regions, when malignant melanomas were localized on the trunk in males. As to the types and the micro-stages of primary tumors, the number of cases collected until now does not permit establishing clear correlations with the incidence of lymph node involvement. Calculating the 5-year-survival rates for patients with and without lymph node metastasis according to the "actuarial method", we found the prognosis to depend largely on the presence or absence of lymph node involvement, even at a time as early as at primary tumor excision. Our results support the indication for prophylactic lymphadenectomy in malignant melanoma, provided the primary tumor has reached or surpassed the micro-stage 3.