Clomiphene, a synthetic non-steroidal agent, when injected into rats at a dose level of 3.0 mg/kg b. w. on days 5, 7 and 9 of pseudopregnancy causes termination of decidual growth. Moreover, its administration on days 12, 14, 16 and 18 of pregnancy causes death and resorption of the foetuses leaving regressing placentae at the sites of their attachment in the uteri. Luteolysis and ovarian poly-follicular conditions were also evident in both instances. Concomitant administration of prolactin or progesterone along with the clomiphene consistently prevented the interruption of clomiphene-induced lysis of deciduoma, gestation and other associated ovarian abnormalities. It is suggested that the abnormal development of the follicular apparatus possibly caused by the clomipheneinduced endogenous FSH during pseudopregnancy or pregnancy is the most likely explanation for the termination of decidual growth or gestation in rats.