The urinary excretion of D-glucaric acid (DGA) has been used as a nonspecific measure of the induction of hepatic enzymes associated with drug metabolism in man. A survey of 124 nonmedicated men (18-56 years of age), who kept a 5-day food and beverage intake record and collected their total urinary output for the last three days of the five, was conducted to assess the relationship between DGA excretion and various dietary factors. Eighteen nonmedicated, healthy women collected the same data, but started recording on the eighth day from the commencement of menstruation. DGA was determined by an enzymatic assay and recorded as micromoles D-glucaro-1,4-lactone/gm creatinine. There was a positive association between total DGA excreted and the use of marijuana, caffeine, and tobacco products, the heaviest users excreting significantly higher levels of urinary DGA than the moderate or low users of the same substance. Analysis of variance of mean DGA excretion also revealed significant differences between females (17.0±3.7) and males (14.3±5.2): male vegetarians (17.4±5.5) and nonvegetarians ( 13.9±5.1) ; and female vegetarians (19.8±4.6) and nonvegetarians (16.2±3.1). Alcohol consumption and family history of cancer incidences were not significantly related to DGA excretion in either sex. Multiple regression analyses revealed that consumption were the two vegetarianism and caffeine strongest predictors of DGA excretion, while alcohol and marijuana consumption affected DGA the least. These results indicate that dietary and environmental factors can exert a significant effect on DGA excretion, and these associations may identify dietary inducers of hepatic enzymes associated with xenobiotic biotransformations in humans.