To establish the age-specific prevalence of urinary symptoms among a community-based cohort of men, a randomly selected sample of men were screened and invited to participate in a longitudinal survey of urinary symptoms. The population of Olmsted County, Minnesota, as enumerated by the Rochester Epidemiology Project, formed the sampling base for this study. Men between 40 and 79 years old with no history of prostate or other urological surgery, and who also were free of conditions associated with neurogenic bladder were invited to participate. A previously validated questionnaire was completed by the subject. Urine flow measures, current medications and family histories of urinary disease were also obtained. Nonresponse corrected scores for a composite of obstructive symptoms showed moderate to severe symptomatology among 13% of the men 40 to 49 years old and 28% of those older than 70 years. Prostatism is a highly prevalent symptom complex among unselected men in the community. The specific urinary symptoms of nocturia, weak stream, restarting, urgency and sensation of incomplete emptying are strongly age-related and, therefore, may be predictive of a prostatic disease process.