To evaluate the penodynamic impact of known vascular risk factors in men with erectile dysfunction, we obtained thorough medical histories covering diabetes, hypertension, heart disease and hypercholesterolemia, alcohol ingestion, and smoking in 265 consecutive patients. We also measured their penile hemodynamic parameters by color duplex ultrasonography after intracavernous prostaglandin E1 injection. In patients with vascular risk factors there was a statistically significant decrease in the peak systolic velocity and increase in the end-diastolic velocity of the cavernosal artery (P < 0.01). Those men who had diabetes had higher average end-diastolic velocities and lower resistance indices (P < 0.01). Smoking and alcohol use also affected penile hemodynamics (P < 0.05). These data confirm that vascular risk factors do increase the likelihood of vasculogenic impotence and that diabetes plays a major role in veno-occlusive dysfunction in the penis.