Recent data suggest that approximately 80 per cent of the men with vasculogenic impotence have evidence of failure to store blood (venous leakage) within the corpora cavernosa. To identify the venous channels into which corporeal blood drains in impotent men, we performed cavernosograms after intracorporeal injection of papaverine in 44 consecutive men presenting with erectile dysfunction and these were compared to studies in 10 potent men. The cavernosograms were examined for evidence of venous drainage from the penis and the site of leakage was identified. It was determined that among the impotent population with vasculogenic impotence 37 of 40 evaluable men (92.5 per cent) demonstrated contrast medium in the venous system draining the penis: the deep dorsal vein was visualized in 55 per cent, proximal cavernosal and crural veins in 55 per cent, deep dorsal and proximal veins in 22.5 per cent and corpus spongiosum in 25 per cent. Only 2 of the 10 potent men demonstrated contrast medium in the venous channels draining the penis. From these observations we conclude that in men suspected of having venogenic impotence identification of the drainage vessels by cavernosography appears to be important in planning any surgical approach to occlude these veins. However, the finding of a venous leak by cavernosography must not be considered a sine qua non diagnosis of venogenic impotence, since a certain percentage of potent men will demonstrate this radiographic finding.