The usefulness of urinary taurine as a non-invasive measure of hepatotoxicity of aflatoxin B1 (AFB1) was evaluated: changes in urinary taurine were characterized in a dose-response, acute toxicity experiment and in two sub-chronic, low dose exposure experiments. Urine of young, male, F344 rats was collected for 4 days prior to, and for 3 days after, the treatment with AFB1. Rats received a single p.o. dose of 0, 0.25, 0.5, 1, 2 or 3 mg AFB1/kg body wt. A transient increase in urinary taurine was noted with doses of 1, 2 or 3 mg AFB1/kg. In two sub-chronic exposure experiments, rats were gavaged with 25 microg AFB1/day for 5 successive days per week for 1 or 2 weeks (approximately 0.25 mg/kg/day). In the first experiment, only a transient increase in urinary taurine during 5 successive doses of AFB1 was observed, while in the second experiment, urinary taurine rose continuously during the 2 weeks of the AFB1 treatment. An explanation for these differing results is not obvious. Urinary taurine appeared to be a useful, non-invasive marker when hepatotoxicity was extensive. Unfortunately, at the low doses of AFB1 (0.25-0.5 mg/kg) as used in carcinogenesis experiments (10 doses of 25 microg/rat), urinary taurine appeared to be an insensitive measure of hepatic damage.