The dorsal and deep arteries are the 2 main blood supplies to the penis. High resolution ultrasonography was used to evaluate the role of these 2 sets of arteries in erection. A total of 44 impotent patients entered this study. We used duplex ultrasonography (Diasonic DRF/400) to assess the role of the dorsal and deep arteries in arteriogenic and nonarteriogenic impotent patients. Vascular velocity, as well as the change in diameter, was recorded before and after an intracavernous injection of 60 mg. papaverine. In the arteriogenic impotence group (28 patients, 63.6%), the velocity increments were 37.1 +/- 23.6 (right side) and 35.4 +/- 17.5 (left side) cm. per second in the dorsal arteries, and 8.3 +/- 5.9 (right side) and 12.6 +/- 5.6 (left side) cm. per second in the deep arteries. In the nonarteriogenic group (16 patients, 36.4%) the velocity increments were 46.5 +/- 25.2 and 41.1 +/- 22.4, respectively, in the dorsal arteries, and 37.3 +/- 16.5 and 37.5 +/- 15.8, respectively, in the deep arteries. Comparison of the velocity increments between the arteriogenic and nonarteriogenic groups revealed no difference in the dorsal arteries (p greater than 0.1) but a significant difference was noted in the deep arteries (p less than 0.01). Similar findings were also encountered when the velocities and diameter increments were compared. This study indicates that the deep arteries have an important role in erectile response, while the dorsal arteries are less important.