One hundred tumours were detected by IV urography and studied by echotomography. In 37 cases, a nephrotomography was performed and in 65 cases a renal arteriogram. The reliability of these three examinations was analysed. Three calcified masses were impossible to analyse by echography and required arteriography from the outset. There were two false negatives related to an error of interpretation and not to any defect in the echography. With regard to the 3 calcified masses, no better information was obtained by nephrotomography. Four necrosed carcinomas were erroneously identified as cysts. Four carcinomas were missed at arteriography. The reliability of echotomography was good apart from in cases of small carcinomas (less than 2 cm) and calcified masses. It proved to be more reliable than nephrotomography and arteriography. By contrast, it was less selective since there were false positive results in 13% of cases.