Marsdenia tinctoria (family: Asclapiadaceae), an indigenous herb of Bangladesh has been used by the shautals of the country to induce abortion. The alcohol extract of the herb and its alkaloidal fraction each showed oxytocic action on sensitized uterine horns of rat. Eight miligram of the extract is equivalent to 0.14 i.u. of oxytocin and 100 mcg of 5-hydroxy tryptamine. The alkaloidal fraction is five times more active than the alcohol extract (400 mcg=0.1 i.u.) of oxytocin. On the contrary, the steroidal fraction of the extract did not have any effect on the contraction of the uterine horns.