Effects of synthetic glucocorticoids and ACTH on the adrenal cortex were studied in 4 cases of cystic ovarian disease (COD) involving 3 cows. Of 2 cases showing anestrus, one was injected intramuscularly (i.m.) with 20mg of betamethasone (Bet) daily for 5 days and the other with 10mg of Bet daily for 4 days. Of the other 2 cases exhibiting symptoms of true nymphomania, one was injected i.m. with 20 mg of Bet daily for 5 days and the other with 10 mg of dexamethasone daily for 4 days. Before and after successive administration with glucocorticoids, 50IU of ACTH was injected i.m. in the 3 cases. The serum concentrations of 11-hydroxycorticosteroids (11-OHCS), progesterone, and proteins were determined daily throughout the experimental period. The response of serum 11-OHCS to ACTH was examined 30 minutes after injection. Glucocorticoids inhibited the release of adrenal corticosteroids in all the 4 cases. A fall of the serum 11-OHCS level was shown earlier after injection with 20 mg of glucocorticoids than after that with 10 mg. Following the termination of injection with glucocorticoids, the serum 11-OHCS level increased remarkably in the 2 cases showing anestrus, but did not in the 2 cases exhibiting true nymphomania. The response of serum 11-OHCS to ACTH was lower in the cows with COD than in control cows with a normal estrous cycle. The serum progesterone level presented essentially the same pattern of fluctuation in response to glucocorticoids and ACTH as the serum 11-OHCS level. Serum proteins decreased slightly after the 4th day of injection with glucocorticoids. From these results, it is suggested that adrenal dysfunction may be related to the different appearence of estrous abnormalities in cows with COD.