The addition of a fluorine atom at position 9α to hydrocortisone, so-called halogenation, increases the anti-inflammatory effect over that of hydrocortisone 7 times, the antirheumatic effect 10 times, and the glycogendepositing effect 13 times, but also increases the sodium-retaining effect to at least 50 times that of hydrocortisone. The addition of a double bond between carbon atoms 1 and 2 to form A 9α-fluorohydrocortisone results in about equal anti-inflammatory and antirheumatic effects but no lessening of the sodiumretaining properties. However, the addition of a hydroxy radical at position 16 to this latter compound, while decreasing considerably the antirheumatic effect (nowfour times that of hydrocortisone), completely neutralizes the salt-and-water-retaining properties, producing in fact what appears to be a sodium-excreting effect. Corticosteroid therapy in the management of rheumatoid arthritis should be undertaken only after serious consideration of the potentialities of the steroid used and the side-effects and other risks involved. It is most important to stress the fact that the degree of intensity of any side-effects that will lead a physician to discontinue the use of a drug, particularly a corticosteroid, is variable. Triamcinolone was found to be supressive of inflammation and rheumatic manifestations in doses roughly proportional to those of prednisone and prednisolone. The advantages of triamcinolone over previously used corticosteroids appeared to be fewer and less severe gastrointestinal symptoms, less psychic irritation, and no effect on arterial blood pressure. It was found, however, to retain many of the troublesome side-effects of the other corticosteroids.