Fifteen patients with sarcomatoid renal cell carcinoma were studied from 1975 through 1987. For each case the radiological, sonographic (US), and histopathological features were reviewed. Neither ivp nor US detected any specific patterns, though demonstrating frequently-necrotic and infiltrating masses. Angiography and/or CT were more useful because they allowed the staging of the tumors and the evaluation of their vascularity. In particular, a frequent correlation was observed between the degree of vascularity and the percentage of sarcomatoid component at histopathology. Sarcomatoid renal cell carcinoma were hypo-avascular in 7 cases and hypervascular in 8. Six of the 7 hypo-avascular cases had a high percentage of sarcomatoid tissue (greater than 50%) and were highly malignant. Seven of the 8 hypervascular neoplasms had a low percentage of sarcomatoid component and presented radiological features similar to clear/granular cell tumors. The survival of the patients with sarcomatoid tumors was much shorter than that of the patients with other kidney carcinomas. Among sarcomatoid tumors, prognosis was worst for the patients with hypo-avascular neoplasms.