The authors examined the association between obesity and lower urinary tract symptoms (LUTS) in the Third National Health and Nutrition Examination Survey. This 1988-1994 US cross-sectional study included 2,797 men aged > or = 60 years whose current weight, weight at age 25 years, highest weight ever, height, waist circumference, and body mass index (BMI) were assessed. LUTS cases had at least three of these symptoms: nocturia, incomplete emptying, weak stream, and hesitancy. Controls were men without symptoms or noncancer prostate surgery. Odds ratios adjusted for age and race and weighted for selection probability were estimated by logistic regression. The odds of LUTS were lower for men who were obese at age 25 years compared with men whose BMI was normal (odds ratio = 0.49, 95% confidence interval: 0.27, 0.91). An increase in BMI between age 25 years and the highest BMI ever was positively associated with LUTS (odds ratio = 1.90, 95% confidence interval: 0.89, 4.05). Men with a larger waist circumference (> or = 102 cm) were more likely to have LUTS compared with men with a smaller waist circumference (odds ratio = 1.48, 95% confidence interval: 0.87, 2.54). Results suggest that being overweight in young adulthood may be associated with a lower prevalence of LUTS later in life, whereas weight gain and central adiposity in adulthood are possibly associated with a higher prevalence of LUTS.