We report that adrenal compensatory hypertrophy occurs in the golden Syrian hamster, an animal secreting cortisol as the primary adrenal glucocorticoid. This response is seen at 3, 6, 10, and 21 days after unilateral adrenalectomy. The response is present in hypophysectomized hamsters and when endogenous ACTH secretion is suppressed by administration of dexamethasone by im injection or by dexamethasone and ACTH using the Alzet osmotic pump. Administration of either aldosterone alone or in combination with dexamethasone and ACTH by Alzet pump completely blocks adrenal compensatory hypertrophy after unilateral adrenalectomy. © 1984 by The Endocrine Society.