Differences of effects between successive administration of whole porcine follicular fluid (WPFF) and charcoal-treated porcine follicular fluid (CTPFF) on the ovary, pituitary and sex steroids of rabbits were investigated. Does of control and each treated group were injected with 4 ml of WPFF, CTPFF or saline, respectively, at 12 hour intervals during 5 days. At the end of the treatment the mean number of all ovarian follicles (≥1.0 mm in diameter) in WPFF-treated does was significantly fewer than those of the other groups. A few large follicles (≥2.5 mm) appeared in this group while we had no large follicles in the other groups. Some of the large follicles were cystic (≥3.0 mm), they were hemorrhagic. The injection of 15 IU hCG for induced ovulation at the end of the WPFF treatment produced no ovulation in 2 does out of the 6 by inspection four days after the hCG injection, while all does ovulated in both the CTPFF- and saline-treated groups. The mean numbers of ovulation by count of corpora lutea in WPFF- and CTPFF-treated does were significantly lower than those in controlled does. Only in non-ovulated does of the WPFF-treated group, large cystic and/or blood follicles appeared. The number of luteal cells per unit area and plasma progesterone levels 4 days after hCG treatment was lower in WPFF-treated does than in the other groups. Vulval swelling and coloration receded l day after beginning of WPFF- or CTPFF-treatment, and estradiol levels in WPFF- or CTPFF-treated does were low during the treatment period. From these results we may conclude that WPFF-treatment exerts more suppressive effect on the female reproductive activity than CTPFF-treatment. In histology of anterior pituitary, basophilic cells which were filled with granules appeared frequently at the end of CTPFF-treatment, moreover degranulation and vacuolization in basophilic cells occurred 36 hours after the end of CTPFF-treatment.