Histomorphic changes in the ovary of Bandicota bengalensis were studied during various stages of the estrous cycle. The ovarian follicles were classified into nine size groups and their frequency distribution was determined for the different phases. In all the ovaries 70% of the follicles were nonantral and below 201 μm in diameter. During proestrus and estrus the ovary possessed the highest number of nonatretic follicles. The follicles ranging above 600 μm were absent at metestrus and diestrus. Preovulatory follicles (>700 μm) were present only during estrus, indicating ovulation during the night of the day of estrus. Excepting the 30- to 50-μm follicles, all other follicles were susceptible to atresia in the cycling rats. Maximum atresia was noticed in the 201- to 500-μm follicles. The number of atretic follicles was highest at diestrus and lowest at estrus. In the continuous diestrous rats, about 50% of the atretic follicles were in the range of 30–100 μm. Three recognizable types of corpora lutea were found in the ovary. The volume of the first and second type corpora lutea was highest at proestrus and estrus, respectively. Mean number of first and second type corpora lutea was 3.87 and 4.56, respectively, and thus about four ova ovulated per ovary during each estrous cycle in this wild rat.