Sixteen Holstein cows with ovarian follicular cysts diagnosed by rectal palpation were used to correlate changes in ultrasonographic image of the ovaries, sexual behavior and skim milk progesterone profiles. Of 16 cases, 4 cows exhibited typical nymphomaniac symptoms, 3 had recurrent nymphomaniac symptoms, and the remaining 9 showed anestrus. Neither corpora lutea nor luteal tissues on the cystic wall were detected by ultrasonography during a 20 days of observation period. On the 20th day the animals were treated with hCG 10, 000 IU. Following hCG treatment, 5 of the 7 nymphomaniac cows no longer showed the symptoms and 3 of the 7 cows showed the formation of corpora lutea or luteal cysts, while 6 of the 7 cows showed an upward tendency of skim milk progesterone levels. Of the 9 anestrous cows, 7 cows responded to hCG with an increase in skim milk progesterone levels and luteinization of co-existing medium-sized follicles and newly-formed follicular cysts. The results indicate that ultrasonography in addition to careful observation of sexual behavior and skim milk progesterone measurement is helpful for an accurate diagnosis of bovine ovarian follicular cysts.