Ovarian hypertrophy is studied by hemispaying the rats for 7, 15, 20, 25 and 30 days. The compensatory hypertrophy of the ovary is calculated in relation to their respective sham operated controls. The maximum hypertrophy is observed 20 days after hemispaying, as indicated by ovarian weight and its histological observations. Thereafter the hypertrophic response though significant, decreases gradually, indicating that once the circulating estrogen secreted by the hypertrophied ovary comes to preoperative level, the pituitary gonadotrophin level also falls down. The hemispaying has no significant effect either on the duration or number of estrous cycle.