The amount of urinary conjugated glucuronic acid excreted by a free-living male population and the effect of certain factors, i.e. vegetable, fruit, meat, and charbroiled food intake, tobacco, alcohol, caffeine, and marijuana use, exposure to chemicals and familial cancer incidence, were investigated. Urine was collected for 24 hours from 117 subjects who complied with the collection protocol and analyzed for each subject. Three days of urine were analyzed for a randomly selected subgroup of forty subjects. For the one-day sample, the mean conJugated glucuronic acid excreted was 0.725 mmole/24 hr or 0.0492 mole/mole creatinine. The values for the three-day sample were 0.848 mmole/24 hr or 0.0562 mole/mole creatinine. An analysis of the one-day data revealed a large degree of between-subject (inter-) variability: 47.1%. The corresponding coefficient of variation for the three-day data was 48.2% when three-day averages were compared. The within-subject (intra-) variability for the three-day data corresponded to a coefficient of variation of 29.2%. The large intervariability probably masked any effects of diet, environment, or genetics upon the observed urinary conjugated glucuronic acid excretion. Caffeine use, vegetable, and fruit intake did show differences between low, moderate, and high consumers, although the biological importance of these associations for the small sample sizes is questionable. Further research regarding conjugated glucuronic acid excretion and dietary, environmental, and genetic influences is therefore warranted. / M.S.