Previous epidemiologic studies evaluating risk factors for lower urinary tract symptoms (LUTS) have focused on White populations. Between September 1996 and January 1998, in a population-based sample of African-American men aged 40-79 years in Flint, Michigan, the authors assessed the role of putative sociodemographic, lifestyle, and medical history risk factors in moderate to severe LUTS, including the subcategories of obstructive and irritative symptoms. After the exclusion of men with prostate cancer or prior prostate surgery and men who were taking alpha-blockers for urinary tract symptoms, 708 participants provided responses to a structured interviewer-administered questionnaire. After multivariable adjustment, current and former smokers were at increased risk of moderate to severe LUTS, including obstructive symptoms. Heavy alcohol consumption and a history of hypertension or diabetes were positively associated with LUTS, and high income (>/=$30,000) was inversely associated with LUTS and with obstructive and irritative symptoms. A history of heart disease was positively associated with LUTS and with irritative symptoms. To the authors' knowledge, this was the first population-based study undertaken in African-American men to evaluate putative risk factors for moderate to severe LUTS, including subcategories of obstructive and irritative urinary symptoms. These results describe associations with specific lifestyle and medical history risk factors.