SummaryBackground: Erectile dysfunction (ED) and cardiovascular disease share common risk factors and may be further aggravated by medical treatment for reducing them.Hypothesis: The study was undertaken to assess the prevalence of ED in patients with diabetes (DM), hypertension (HTN), or both diseases, and to evaluate the effect of patient age, medical treatment, and disease duration and control on the prevalence of ED in this population.Methods: A group of 150 primary practitioners who had patients with known DM and/or HTN conducted a survey, utilizing IIEF-15, a 15-item multidimensional, self-administered questionnaire used for the clinical assessment of ED.Results: In all, 1,412 patients were included: 37% had DM, 38% had HTN, and 25% had both diseases. Their mean age was 55, 58, and 60 years, and 62, 46, and 67% had some degree of ED, respectively. The prevalence of ED increased with age and disease duration in each age group and was higher in subjects with DM than in those with HTN, especially in those aged < 65 years. Poor glycemic control was associated with a higher prevalence rate of ED early in the course of the disease. There was no significant difference in the prevalence of ED according to type and number of antihypertensive drugs.