BACKGROUND AND AIMS: A High carbohydrate diet induces pigmeni gallstones in hamsters, but the mechanis has not been determined. It has been suggested that free radicaL play a role in the formation of pigment gallstones. This study was designed t v investigate whether antioxidants (allopurinol and vitamin E) would reduce the formation of pi,ment gallstones and there was the evidence of the action of free radicals. METHODS: Seventy three ale hamsters were divided into four groups: group I (n=19) was fed on normal rodent chow (l3% carbohydrate), group II (n= l7) was fed on a high carbohydrate diet (65% carbohydrate), group III (n=19) was fed on a high carbohydrate diet containing 0.2% allopurinol, and group IV (n=18) was fed on a high carbohydrate diet containing 1% vitamin E. After six weeks feeding, the animals were sacrificed, the incidence of gallstones was checked grossly, and malondialdehyde levels were measured in liver tissue and bile juice of hamsters. RESULTS: Gallstones developed in 0% of group I, 29.4% of group II, 38.9% of group III, 10.5% of group IV (group I vs II, III: p<0.05). There was no difference in the malon-dialdehyde levels of liver tissue among four groups. Malondialclehyde levels of bile juice in group III and IV were lower than those in group 1 (p<0.05), but the e was no difference among group II, III and IV (p>0.05). Also there was no difference in the malcndialdehyde levels of liver tissue and bile juice between positive stone group and negative stone group (p>0.05). CONCLUSIONS: Allopurinol and vitamin E did not reduce the formation of pigent gallstone and evidence was not found that free radicals play a key role in the formati n of pigment gallstones in high carbohydrate diet-fed hamsters.