Summary Several diets were tested for adequacy in the nutrition of the guinea pig, and the necessity of the grass juice factor for this animal was confirmed. A diet high in the grass juice factor and adequate for normal guinea pigs, failed to maintain adrenalectomized guinea pigs given amounts of desoxycorticosterone acetate which were adequate when a normal diet was fed. Adrenalectomized guinea pigs can be maintained for at least 6 weeks on a normal diet if salt drinking fluid is offered. Desoxycorticosterone acetate subcutaneously administered in daily doses of 0.5 to 1.0 mg produces normal growth in adrenalectomized guinea pigs. Even though adrenalectomized guinea pigs had been maintained for over 5 months by salt and hormone therapy, they died on an average of 4.6 days after discontinuing this therapy.