OBJECTIVE We assessed the morphodynamic features of cavernous arteries and helicine arterioles by power Doppler sonography in vasculogenic and nonvasculogenic impotent men. METHODS A total of 40 impotent patients with and without definite vascular risk factors were studied by penile power Doppler sonography. The test was performed during penile flaccidity, after intracavernous injection of 20 mcg. alprostadil and after subsequent genital and audiovisual sexual stimulation. A second injection and stimulation were given if the erectile response observed after the initial injection was less than the maximum erection seen during sexual activity. Morphodynamic parameters evaluated by power Doppler imaging included vessel course, shape, wall thickness and pulsatility, peak systolic velocity, end diastolic velocity, acceleration time and resistance index. RESULTS In the nonvasculogenic group all patients who achieved rigid erection showed normal cavernosal artery and helicine arteriole inflow. In these cases the arteriolar picture was characterized by the presence of 3 orders of distal ramifications originating from the cavernous arteries with an acute angle, systolic diastolic flow during penile tumescence and systolic flow alone at full rigidity. In the vasculogenic group patients with normal cavernous artery inflow showed an arteriolar tree that was pathological in 50% and was characterized by a reduced number of ramifications originating perpendicularly from the cavernous arteries and irregular caliber (arteriolar impotence). In the same group patients with reduced cavernous artery inflow also showed normal or pathological arteriolar components (pre-penile arterial impotence and diffused penile arterial impotence). CONCLUSIONS Power Doppler sonography allows a precise study of the morphodynamics of the cavernous arteries and helicine arterioles. Our preliminary data suggest that the intracavernous arteriolar component may have a significant role in the genesis of some forms of vasculogenic impotence.