Four successive solvent extracts of the whole plant Striga orobanchioides have been screened for antifertility activity in albino rats. Of these the ethanolic extract was found to be most effective in causing significant anti-implantation activity. The antifertility activity was reversible on withdrawal of treatment with the extract. The ethanolic extract at 200 mg/kg showed estrogenic activity. Histological studies of the uterus were carried out to confirm this estrogenic activity.