The metabolism of Cortisol in the normal Romney ewe was investigated by analysis of the radioactive metabolites excreted in the urine following intravenous (I.V.) administration of 4-c14 cortisol. The metabolite glucuronic!os were hydrolysed with b-glucuronidase and extracted from the aqueous medium with ethyl acetate. The neutral fraction was divided into c-19 and c-21 metabolites by sequential elution from a florisil column. Extensive use was made of T.L.C. for the separation and analysis of each fraction before the quantitation of individual components. A series of experiments was performed with, surgically modified sheep involving collection of bile and urine both after I.V. injection of 4-c14 cortisol, and after intraduodenal infusion of radioactive biliary metabolites obtained from I.V. administration of 4-c14 corticol. The metabolites collected at each stage were analysed both qualitatively and quantitatively. The urine collected each hour for 18 consecutive days from a normal sheep, was subjected to colorimetric determination for a-ketol and 17-ketogenic steroid content. The data obtained was analysed for diurnal variation in chromogen output, and the daily secretion rate of cortisol was estimated.