Abstract: The ethanol extract of Pergularia daemia and its steroidal fraction are reported to have antifertility activity. In this work we studied the alkaloidal fraction of the ethanol extract to observe its antifertility activity. Oral administration of the alkaloidal fraction at a dose of 200mg kg‾1 body weight showed a significant activity in preimplantation stage of female mice. The activity of the alkaloidal fraction, when compared with the steroidal fraction, was found to be more pronounced since the former inhibited not only the fertility of the female mice but also took short period to return the oestrous cycle to normal, with in 4 to 6 days of drug treatment while steroidal fraction treated mice returned to normal within 6 to 8 days.