Effects of choleresis produced by atropine (4-10(-4)M) on the biliary elimination of 3H-ouabain and on the biliary clearance rate of 14C-erythritol were studied in the isolated perfused rat liver. The increased bile flow produced by atropine was associated with decreased level of 3H-ouabain in the bile. The cumulative biliary elimination of ouabain was not affected. Atropine choleresis caused an increase in the erythritol clearance rate and a reduction in the bile to plasma ratios of erythritol as compared to the controls. The results suggest that the choleresis induced by atropine is not entirely of canalicular origin but possibly reabsorption mechanisms in the bile ducts or ductules are also involved.