Objectives: To measure the prevalence of erectile dysfunction (ED) in community-based populations in Brazil, Italy, Japan, and Malaysia and to study its association with the demographic characteristics, medical conditions, and health-related behavior.

Methods: In each country, a random sample of approximately 600 men aged 40 to 70 years was interviewed using a standardized questionnaire. All the data were self-reported. ED was assessed by the participants' "ability to attain and maintain an erection satisfactory for sexual intercourse," and the men were classified as not having ED if they answered "always" and as having mild, moderate, or complete ED if they answered "usually," "sometimes," or "never," respectively.

Results: The age-adjusted prevalence of moderate or complete ED was 34% in Japan, 22% in Malaysia, 17% in Italy, and 15% in Brazil. The overall age-specific prevalence of moderate or complete ED was 9% for men aged 40 to 44 years, 12% for 45 to 49 years, 18% for 50 to 54 years, 29% for 55 to 59 years, 38% for 60 to 64 years, and 54% for those 65 to 70 years. The increased risk of ED was associated with diabetes, heart disease, lower urinary tract symptoms, heavy smoking, and depression and increased by 10% per year of age. It was inversely associated with education, physical activity, and alcohol drinking.

Conclusions: ED is an international problem, the prevalence and severity of which increases with age. Despite national variations in prevalence, uniform associations were found between ED and medical conditions and lifestyle habits.