We investigated the influence of the hydrophilic bile acids (cholic and ursodeoxycholic) and hydrophobic (chenodeoxycholic and deoxycholic) on the bile secretion during the isolated rat liver perfusion to find out the role of the bile acids detergent properties in their choleretic and cholestatic effects. The increase of the concentration of the hydrophobic bile acids changed the type of the bile secretion rate dynamic from one- to two-peak stimulation. It was shown that the difference in the rate of the bile acids biotransformation was essential both in this process and in the possibility of the bile acids to cause the cholestasis. It was evaluated the bile acids osmotic activity under the micelle formation and micelle information conditions. It was shown the significance of the other bile acids effects but direct osmotic on the osmotic gradient development.