Benzene disposition and metabolism were examined as a function of age in male C57BL/6N mice aged 3 and 18 months. Mice received a single oral dose of either 10 or 200 mg/kg (14)C-benzene (approximately 25 microCl/kg). Excretion of (14)C-derived benzene radioactivity (RA) was monitored in urine, feces, and as exhaled (14)CO2 from 0 to 72 hr, and as exhaled unmetabolized benzene from 0 to 6 hr. At 10 mg/kg (14)C-benzene, urinary elimination was the major route of excretion in both 3- and 18-month mice. Urinary excretion of (14)C-derived benzene RA was significantly decreased in 18- vs. 3-month mice at 4, 6, 24, and 48 hr, while fecal excretion was significantly increased at 72 hr. Elimination of (14)C-benzene as (14)CO2 and unmetabolized (14)C-benzene was also increased in 18- vs. 3-month mice at this dose. The results of these experiments indicate that total metabolism of benzene as well as metabolism to specific metabolites is affected by aging. (Copyright (c) 1991 by The American Society for Pharmacology and Experimental Therapeutics.)