In order to establish a profile of detoxification via glutathione conjugation, the level of urinary mercapturic acid excreted by a free-living male population and the effect of external environmental and genetic factors, such as consumption of vegetables, fruits, and meat, charbroiled food intake, tobacco, alcohol, caffeinated coffee, and marijuana use, exposure to chemicals and familial cancer incidence, were investigated. A subgroup of 30 subjects was randomly selected from 117 subjects who complied with the collection protocol. Three consecutive 24 hr urine samples of this subgroup were analyzed. The modified method of Seutter-Berlage et al (Chemical Porphyria in Man. Elsevier/North-Holland Biomedical Press, N.Y. 1979:233-236) was used for the quantitation of urinary mercapturic acid. The mean excretion of mercapturic acid was 0.27 mmole mercapturate (-SH)/24 hr and 18.1 umole -SH/mmole creatinine. An analysis of variance showed a large degree of inter- and intraindividual variability. The interindividual coefficients of variation in mmole -SH/24 hr and umole -SH/mmole creatinine were 37.7% and 31.2%, respectively. The intraindividual coefficients of variation in mmole -SH/24 hr and umole - SH/mmole creatinine were 32.4% and 30.1%, respectively. A higher (p≤0.05) excretion of mercapturic acid was observed among subjects with a high frequency of exposure to chemicals. The lack of significance of the other dietary, non-dietary, and genetic factors on the observed mercapturic acid excretion may be due to the large inter- and intravariability, the use of food consumption frequency in food intake analysis, and unequal sample sizes of subgroups. / Master of Science