Endometrial histology in baboons (Papio cynocephalus anubis) was evaluated after five days of clomiphene citrate (CC) treatment initiated on either cycle day six (n = 8) or ten (n = 4). Biopsies performed before and after a human chorionic gonadotropin (hCG) induced ovulation were compared to non-CC treated controls. Although CC had a definite antiestrogenic effect on perineal skin, no significant effect of endometrial proliferation was demonstrable.