To investigate the prognostic value of tumour vascularity we studied 84 patients with primary melanomas ranging in tumour thickness (Breslow) from 0.37 to 7 mm and in depth of tumour infiltration (Clark) from II to V. Vascularization was assessed by immunohistochemistry with a CD-31 antibody recognizing endothelial cells. The CD-31-positive vessels were counted and the degree of vascularization was correlated with the survival of the patients. In addition, the relationship between blood vessel density and some histopathological data is discussed. In our study, the multivariate Cox model showed that the only independent variable in disease-free survival was tumour thickness (Breslow classification) and the only one in overall survival was depth of tumour infiltration (Clark classification). In disease-free survival, tumour thickness (Breslow classification) was a clear prognostic factor (P = 0.004) after 4 years' follow-up, as were depth of tumour infiltration (Clark classification) (P = 0.04) and ulceration (P = 0.04). In overall survival, tumour vascularity was the strongest prognostic factor at 4 years, high vascularity being associated with a good prognosis (P = 0.06). Clark classification was also a prognostic factor (P = 0.02) in overall survival. We conclude that high vascularization is associated with a better prognosis but is not an independent prognostic indicator.