OBJECTIVE Endothelin and nitric oxide (NO) are modulating factors of vascular tonus. Recent data have given support to the assumption that penile erection is the consequence of competition of vasodilator NO and vasoconstrictor endothelin on penis. Reported that atherosclerotic vascular disease is presented with increased endothelin and decreased NO release, this study was designed to search for a similar endothelin alteration in corpus cavernosum of penis. METHODS Intracavernosal entothelin levels of 33 important men with arteriogenic impotence before and after papaverine-induced penile erection were examined by using radioimmunoassay kits. RESULTS The intracavernosal endothelin levels of arteriogenic impotent men in our study were not altered both in the flaccid and papaverine-induced erectile state. CONCLUSIONS The lack of alteration was concluded to be the possible result of cavernosal damage in arteriogenic impotence leading to diminished release of NO and increased release of endothelin.