We conducted an international comparison of the prevalence of urinary symptoms of prostatism in 4 countries, using a community-based random sampling of subjects, similar study procedures, and a single definition of cases that was based on a standardized symptom questionnaire. In Scotland 1,994 medically eligible men aged 40-79 years agreed to participate from 3 communities of the Forth Valley. In France, a nation-wide survey was conducted cross-sectionally in a representative sample of 2,011 French men aged 50-84 years. In the USA, the Olmsted County (OC) study recruited an age- and urban/rural-stratified random sample of 2,115 county residents drawn from medically eligible men aged 40-79 years. In Japan, 290 men aged 40-79 years from a fishing village participated in the study. Response rates were 55, 53, 55, and 43% in Scotland, France, OC and Japan, respectively. Urinary symptoms were assessed by the International Prostate Symptom Score (I-PSS), after metrologic validation in English and cross-cultural adaptation of the questionnaire. The prevalence of moderate to severe symptoms (I-PSS > 7) were 14, 18, 38, and 56% in France, Scotland, OC and Japan, respectively. This pattern was consistent within decades of age, and was found for most of the individual urinary symptoms. The proportion of men in Japan reporting very low I-PSS (0 or 1) was approximately 2, 4 and 8 times less frequent, than in OC, Scotland, and France, respectively. Differences in the prevalence of reported urinary symptoms might reflect between-country differences in the true prevalence of benign prostatic hyperplasia. However, cross-cultural differences in the perception and/or willingness to report urinary symptoms may play an important role in the observed differences. Further study will be required to elucidate the underlying causes of the observed differences.