The vascularity of 107 primary cutaneous melanomas has been characterized by morphometric histological analysis. The lesions selected for study were of thickness 0.85-1.25 mm and the aim was to evaluate the prognostic significance of tumour vascularity. Two groups of patients were identified; 86 with no evidence of recurrence after a minimum follow-up period of 5 years and 21 with locoregional recurrence and/or metastasis. The lectin Ulex europaeus type I was used for endothelial cell staining of tissue sections and morphometric analysis was performed to derive the vascular length, surface and volume density from independent measurements of tumour, adjacent dermis and the junctional zone between tumour and underlying tissue. A wide range of values was obtained for each parameter with increased vascularity always found at the tumour base compared with the tumour as a whole. In relation to the adjacent normal dermis, vascularity was generally found to be higher at the tumour base but either higher or lower in the tumour overall. Tumour recurrence could not be predicted by any of the derived vascular parameters either independently or together with other histological and clinical features. This study suggests that tumour vascularity is of no prognostic significance in melanoma of the above thickness range. The highly variable extent of tumour vascularity was not correlated with other clinical or histological parameters, but may have implications for the delivery of pharmaceutical agents used for diagnosis or therapy.