1. The effect of adrenotropic extracts of the pituitary upon the prostate and seminal vesicles of castrate young rats, previously reported, has been confirmed. 2. The response may be elicited in hypophysectomized animals. 3. The adrenotropic extract is without effect in adrenalectomized castrated rats. 4. The adrenotropic extract used causes marked enlargement of the adrenal cortex in normal animals, and not only prevents the adrenal atrophy following hypophysectomy but enlarges the cortex to more than twice the normal size. Some changes in the medulla of the adrenal are also reported.