One hundred impotent men were evaluated with Doppler pulse-wave analysis and intracavernous papaverine. Fifty-four men with normal Doppler study response had abnormal responses to papaverine. A normal Doppler study response failed to predict the inability of papaverine to induce an erection in 54 per cent of cases. Twenty-seven patients had abnormal Doppler study responses, and only 2 of these men had a normal response to papaverine. An abnormal Doppler study response was highly predictive of a vascular abnormality.