Our objective was to analyze the prevalence and risk factors for erectile dysfunction (ED) in men with diabetes in Italy in a cross-sectional study. Eligible for the study were men aged 20-69 years with a diagnosis of IDDM or NIDDM who were observed on randomly selected days in 178 diabetes centers in Italy. ED was defined as a failure to achieve and maintain an erection sufficient for satisfactory sexual performance. Of the 9,868 diabetic men interviewed, 3,534 (35.8%) reported ED. The prevalence increased with age, from 4.6% in men aged 20-29 to 45.5% in those aged > or =60 years (test for trend, P = 0.0001). After taking into account the confounding role of age, men with NIDDM reported ED less frequently than did men with IDDM (odds ratio [OR], 0.7; 95% CI 0.6-0.8). In comparison with men reporting diabetes lasting < or =5 years, the ORs for ED were 1.3 and 2.0 for subjects with diabetes lasting 6-10 and 11-30 years, respectively. In comparison with men with good metabolic control, the ORs for ED were 1.7 and 2.3 in men with fair and poor control, respectively. A history of diabetes-related arterial, retinal, or renal diseases and neuropathy was associated with an increased risk of ED. Finally, in comparison with never-smokers, the ORs for ED were 1.5 (95% CI 1.3-1.6) for current smokers and 1.4 (95% CI 1.3-1.6) for ex-smokers. The OR increased with number of cigarettes smoked per day: in comparison with men smoking <12 cigarettes per day, the OR was 1.5 (95% CI 1.3-1.7) for those smoking > or =30 cigarettes day. The study offers a quantitative estimate of the prevalence of ED and of its main risk factors in Italian men with diabetes.