The risk of liver cancer is greatest in people both infected with hepatitis B virus (HBV) and highly exposed to aflatoxin B(1) (AFB(1)). The tree shrew (Tupaia belangeri chinensis) is a unique species that can be infected with human HBV, is susceptible to AFB(1)-induced liver cancer, and shows a synergistic interaction between HBV and AFB(1) for liver cancer. In this regard, the tree shrew may be useful for evaluating experimental chemoprevention strategies relevant to high-risk human populations as it mirrors the human epidemiology of liver cancer. To begin developing the model for chemoprevention study, two groups of tree shrews were fed 400 microg AFB(1)/kg b.wt. in milk daily for 4 weeks. One week prior to AFB(1) administration, one group also received oltipraz (0.5 mmol/kg, p.o.) daily for 5 weeks. At weekly intervals, 1 ml of blood and a 24-h urine sample were obtained from each animal. Aflatoxin-albumin adducts in serum were determined by a radioimmunological assay and aflatoxin-N(7)-guanine adducts in urine were measured by HPLC. Aflatoxin-albumin adducts increased rapidly in 2 weeks to plateau at 20 pmol/mg protein, and they diminished after cessation of AFB(1) exposure. Oltipraz significantly attenuated the overall burden of aflatoxin-albumin adducts throughout the exposure period with a median reduction of 80%. In a single cross-sectional analysis at the end of AFB(1) dosing, oltipraz treatment decreased urinary aflatoxin-N(7)-guanine by 93%. Collectively, these results indicate that oltipraz reduces AFB(1) risk biomarkers in the tree shrew in a manner similar to that observed in rodents and humans, and establishes a rationale to evaluate cancer chemoprevention by oltipraz in human HBV-infected, AFB(1) exposed tree shrews.