The effects of clomiphene citrate (0.3 or 3.0 mg/kg body weight/day) for 10 consecutive days on the ovary of a wild rat, Bandicota bengalensis, were studied. The low dose of clomiphene decreased the number of nonatretic follicles larger than 400 µm in diameter, increased atresia in follicles smaller than 200 µm, inhibited granulosal mitosis in follicles less than 200 µm and between 401 and 600 µm in diameter and inhibited thecal mitosis in follicles smaller than 400 µm and larger than 600 µm. The high dose of clomiphene increased the number of follicles between 201 and 400 µm, decreased the number of follicles larger than 600 µm, increased atresia in follicles of 51–400 µm and increased granulosal mitosis in follicles of 201–400 µm diameter. In both the doses, clomiphene inhibited the ovulation rate (p < 0.005), with 25 and 35% of the rats being anovulatory in low and high doses, respectively. In addition, clomiphene caused irregularity in the estrous cycles associated with increased cycle length. These results suggest that the clomiphene-induced partial inhibition of ovulation is possibly through its action on follicular growth and atresia mainly in nonantral ( < 200 µm) and mature follicles (401–600 µm).