The effect of adrenalectomy on taurocholic acid, the main bile acid of the rat, was studied. The bile was obtained by cannulation from the ductus choledochus. The concentration of taurocholic acid in the bile was determined using thin-layer chromatography. The taurocholic acid concentration in the bile of the adrenalectomized animals was significantly decreased, being about a half that of the control rats. The results are briefly discussed.