The plasma concentrations of free 17,21-dihydroxy-20-ketosteroids and urinary excretion of both free and glucuronide forms have been determined after oral, intramuscular, and intravenous administration of cortisone, hydrocortisone, their δ1 forms, and 9α-fluorohydrocortisone to dogs. Excretion of the glucuronide forms of those steroids with a double bond at the 1-2 position or with a fluorine at position 9 was depressed, and the plasma half-life of each of these steroids was longer than that of the parent compound.