The objective was to study the risk factors in patients with erectile dysfunction in correlation with ultrasound findings of penile vasculature. Patients with erectile dysfunction were classified in four groups according to their risk factors. Group A (37 pts) who were heavy smokers, group B (40 pts) who suffered from diabetes mellitus, group C (30 pts) who suffered from hyperlipidemia and group D (40 pts) with no risk factors. The peak systolic velocity (PSV) was measured after the intracavernous injection of 10 mg alprostadile. Normal values were PSV>35 cm/s and endiastolic venous velocity<4 cm/s. It was found that the mean PSV in group A was 22.2+/-2.25 cm/s without venous leakage, in group B the mean PSV was 24.6+/-1.29 cm/s but there was a significant venous leakage (mean end-diastolic velocity 6.2+/-1.37 cm/s). Patients with hyperlipidemia (group C) had a mean PSV of 26.2+/-1.74 cm/s and insignificant venous leakage and patients in group D had a normal vascular profile. Patients with erectile dysfunction who are heavy smokers are predisposed to have penile arterial insufficiency, while diabetics have both arterial insufficiency and venous leakage.