In a retrospective study of 95 patients seen between 1950 and 1978, the outcome of malignant melanoma levels III, IV and V of Clark's classification was reviewed. Patients with lentigo malignant melanoma were excluded. The overall survival rate was 63% at 5 years and 48% at 10 years. For the whole population of patients significant differences in survival rate were associated with level (p = 0,00002), thickness (less than 2 mm or greater than or equal to 2 mm; p less than 0.0,0001) and histological type (p = 0,02). The significance of prognostic variables taken separately was calculated by the Breslow method and was found to be: p = 0,0005 for thickness, p = 0,0009 for patient's age and p = 0,02 for histological type. In analysis with two variables, including level, thickness was the variable that added most to the information on prognosis supplied by level. For the population of patients with melanoma levels III and IV significant differences in survival rate were associated with thickness (less than 2 mm or greater than or equal to 2 mm; p less than 0,001), though not with level. When the variables were studied separately, thickness and patient's age were significant (p = 0,02 and p = 0,03 respectively). Analysis with two variables, including thickness, showed that age was the variable that added most to the information on prognosis supplied by thickness.