This study was performed to determine the contribution of the extrahepatic bile ducts to bile flow in the rhesus monkey. Bile flow from the 2 sides of the liver was divided. The major extrahepatic bile ducts remained connected to one side of the liver only. Bile flow, and the concentrations of [14C]erythritol, bicarbonate, bile acid, and bilirubin in bile samples from the 2 sides of the liver, in the fed state were measured and compared. An estimate of the net flow from the extrahepatic ducts was obtained from the [14C]erythritol concentrations on the 2 sides of the liver and the bile flow rate on the side with the extrahepatic ducts. The [14C]erythritol bile plasma ratio was significantly lower in bile collected from the side with the extrahepatic bile ducts, than in bile from the other side of the liver. About 10% of total hepatic bile flow originated in the extrahepatic bile ducts, in the fed state. The bicarbonate [14C]erythritol concentration ratio was significantly higher in bile from the side with the extrahepatic bile ducts. Bicarbonate bile acid, and bicarbonate bilirubin concentration ratios were also significantly higher in bile from the side of the liver with the extrahepatic ducts. The extrahepatic bile ducts have a physiologically significant role in the secretion of bile water. Bicarbonate is secreted in association with water in the extrahepatic ducts.