Changes of bile composition in gallbladder bile and serum chemistries were investigated in nine dogs after proctocolectomy and ileoanal anastomosis, using an interposed jejunal segment as a neorectum. A significant decrease in cholic acid and an increase in deoxycholic acid were observed 24 weeks after the operation, although there was no significant change of total bile acid and phospholipids in the bile. Concentration of cholesterol and cholesterol saturation index in bile increased after total proctocolectomy. Although serum triglyceride levels became lower compared with the nontreated control group, concentrations of total protein, serum cholesterol, total lipids, blood sugar, and electrolytes showed no significant difference. This operative procedure apparently did not impair intestinal absorption of bile acid, but did increase the biliary cholesterol saturation index.