The metabolism of i.v. administered hydrocortisone-4-14C 21-sulfate was studied in 2 subjects.The 1st subject excreted 65% of the radioactivity in the urine in 3 days; an insignificant amount was present as glucosiduronate and the major portion was presented as sulfate ester.Recovery of hydrocortisone 21-sulfate was 43% and a very small amount of 3α,11β,17,21-tetrahydroxy-5β-pregnan-20-one (I) was found in the sulfate fraction.The 2nd subject received hydrocortisone-1,2-3H simultaneously.The hormone was metabolized in a normal manner.Of the hydrocortisone sulfate given, 79% of the 14C was recovered in the urine and 23% of the dose was present as glucosiduronate.The principal portion of this radioactivity was in the 17-ketonic metabolites; there was essentially no conversion to 3α,17,21-trihydroxy-5β-pregnane-11,20-dione (II) and a very small amount to I.Thus, hydrocortisone 21-sulfate is a poor precursor of II glucosiduronate and I glucosiduronate and does not contribute significantly to the discrepancy observed in sp. activity of these metabolites following tracer hydrocortisone in production rate determinations