The objective of these studies was to investigate the comparative physiology and regulation of bile acid metabolism in the male Golden Syrian hamster by measuring the rate of fecal bile acid excretion and bile acid pool size in animals fed a cereal-based diet either alone, or with added cholesterol or cholestyramine. In group-housed hamsters fed only the plain diet fecal bile acid excretion in animals at 6, 10, and 15 weeks of age averaged 11.0, 8.0, and 6.9 μmol/d per 100 g body weight (bw), respectively. Pool size, measured by subtracting from the total amount of bile acid washed out over 12 hours of biliary diversion the amount of bile acid excreted in the stools over the same period, equalled 17.8 μmol/100 g bw in 15-week-old hamsters fed the plain diet. Hence, under basal conditions, these animals turned over about 38% of their bile acid pool daily. In hamsters fed a diet with 3% cholestyramine for 18 days, fecal bile acid excretion averaged 20.6 μmol/d per 100 g bw, and the pool size contracted to 5.8 μmol/100 g bw. In matching animals fed a diet containing 0.12% cholesterol for 30 days, hepatic cholesterol levels increased from 1.9 ± 0.1 to 12.6 ± 0.7 mg/g, fecal bile acid excretion increased marginally from 5.8 to 8.0 μmol/day per 100 g bw, while pool size was unchanged (16.6 μmol/100 g bw). When the cholesterol content of the diet was raised to 1.0%, hepatic cholesterol levels reached 66.5 ± 2.6 mg/g, but bile acid excretion remained at 8 μmol/d per 100 g bw. These data define some of the basal features of bile acid metabolism in the hamster, and substantiate the view that the marked cholesterolemic response of this species may relate partly to a limited ability to convert dietary cholesterol to bile acid.