Effects of green tea catechins onN-nitrosobis(2-oxopropyl)amine (BOP)-induced oxidative stress in pancreas and liver were examined. Hamsters were divided into two groups: one group was given free access to a 0.1% solution of green tea catechins as drinking water (c-ham) and the other to plain tap water (w-ham) for 1 week before subcutaneous injection of BOP 20 mg/kg body weight. Zero, 1, 2, 6, 12, 24, and 48 h after BOP injection, the pancreas and liver were excised and the tissue concentration of lipid peroxides (TBA values) and the amount of 8-hydroxydeoxyguanosine (8-OHdG) in nuclear DNA were measured. The concentration of lipid peroxides and the amount of 8-OHdG in the pancreas showed similar patterns of change between c-and w-ham. Soon after BOP injection, the concentration of lipid peroxides and the amount of 8-OHdG increased with a peak at 1 and 6 h, respectively. Their peak values of c-ham were significantly depressed compared with those of w-ham. Both levels returned to steady-state levels by 24 h. In the liver, the concentration of lipid peroxides and the amount of 8-OHdG were not affected by BOP administration. These results suggest that BOP induces oxidative damages in the target organ and oral intake of green tea catechins has a protective effect on the oxidative stress.