The effect of aqueous extract of Moringa oleifera Lam. (roots) has been studied on histoarchitecture of the uterus during pre and post-implantation stages in rats so as to elucidate its antifertility mode of action. The histoarchitecture of the uterus of control pregnant rat had revealed a clear-cut close apposition of the uterine endometrium with reduced lumen and loose stroma. There was a prominent appearance of deciduoma and the uterine glands were enlarged. Glandular cells showed hypertrophy and in the endometrium the leucocytic infiltration was increased. When the aqueous extract of M. oleifera Lam. was administered, no deciduoma was observed on day 5th of pregnancy and the luminal epithelium remained unstimulated. The lumen was enlarged and the uterus was non-oedematous. It has been concluded that the administration of aqueous extract of M. oleifera Lam. to pregnant rats could not stimulate the uterus which remained non-receptive throughout the period of treatment, therefore, the fertilized eggs may not be welcomed by the unprepared uterus.