Angiogenesis is an essential process in the progression of malignant tumors. Tumors of the ureter and renal pelvis account for 5% of all urinary tract neoplasms. Little is known about angiogenesis in upper urinary tract urothelial tumors. We tried to demonstrate angiogenesis by using three endothelial markers CD31, CD34, von Willebrand factor and one pericytes marker (alpha-smooth muscle actin) in 26 cases. The pattern of CD31 immunolabelling was more complex and extensive than the vessel pattern shown by CD34 or factor VIII staining. In non-invasive tumors we observed that angiogenesis process is limited to connective tissue of tumor stroma. In the tumor area, the blood vessels stained with anti-CD31 had large lumen, thin walls and numerous branches, some of them being very thin. Pericyte covered vessels were branching of frequently into smaller, pericyte negative vessels.