Introduction: Erectile dysfunction (ED), is defined as the inability to maintain an erection sufficient to permit satisfactory sexual intercourse. More than a half of men aged between 40-70 years have erectile dysfunction (ED). As the erectile physiology has been better understood and new treatment strategies have been introduced patient» complaining of ED have increased in number. Diabetes Mellitus (DM), hypertension (HT) and cardiovascular diseases (CVD) are most important risk factors related to ED. Penile color Doppler ultrasonography (CDU) is minimally invasive diagnostic tool for vasculogenic ED. Our aim is to study the relationship between risk factors for ED and vasculogenic etiology. Materials and Methods: Between January 1997 and June 2003, 118 patients with ED are enrolled into the study. Patients were divided into 3 groups; patients with DM, patients with CVD involving coronary heart disease and/or HT and patients with no known risk factor. All patients underwent penile CDU. First minute peak-systolic and 20th minute end diastolic flow rates were recorded in each patient. Risk groups were compared according to ages and penile CDU findings. Results: Mean age of all patients was 52.4±13.1 years. Of 118 patients, 18 patients were in DM group, 32 patients were in CVD group and the remaining 68 patients had no risk factor. DM group was younger than CVD group (42.5±8.9 years vs 62.8±5.9 years; p<0.05). First minute peak systolic flow rate was the lowest in DM group (p=0.028). There was no significant difference in 20th minute end diastolic flow rate between groups. Conclusion: ED prevalence increases with age and underlying comorbid diseases. DM may influence the erectile vascularity in younger ages. Erectile vascular system is under the risk at older ages. Penile CDU is a recommended diagnostic tool for vasculogenic pathology related to ED risk factors.