The incidence of cutaneous malignant melanoma in the Caucasian population has continued to increase at an alarming rate and is expected to be 1 in 75 by the year 2000. Within the medical community, these trends have prompted an interest in factors that potentially influence the biologic activity of such lesions. Several clinical and pathologic variables have been identified that affect the progression and behavior of melanoma. On the basis of multivariate analysis, the most important factors for predicting survival in patients with stage I and II melanomas are tumor thickness, presence of ulceration, and anatomic site of the primary tumor (the prognosis is poorer with head and neck lesions than with extremity lesions). For patients with stage III melanomas, all the foregoing factors plus the extent of nodal disease are of prognostic importance. For patients with stage IV melanomas, the main prognostic factors are the number of metastatic lesions and the site of metastatic involvement (visceral lesions portend a poor outcome).