In a retrospective study of 324 cutaneous malignant melanomas in stage I, treated during the years 1959-74, the influence of different morphological and clinical factors on the prognosis was investigated. 223 patients with melanoma in levels II-V, observed for more than five years, were subjected to a multivariate analysis. 180/223 were in levels III-V. The age of the patient, the location of the tumour, its diameter, thickness, infiltration level, presence of ulceration and mitotic activity were shown to be of significant importance for the five-year survival of the 223 patients. Analysis limited to levels III-V disclosed that the diameter and the thickness of the tumour but not the infiltration level significantly influenced the prognosis. However, the sex of the patient, the histogenetic type of the tumour, the cross-sectional profile, vascular invasion and degree of lymphocytic infiltration did not correlate with survival.