The bark extracts of Prosopis staphaniana have been investigated for their anthelmintic activity aganist Pheretima posthuma. The different concentrations of each extract have been studied in the bioassay, which exhibited a dose dependent inhibition of spontaneous motility (paralysis) and evoked responses to pin-prick. At higher doses the effects were comparable with that of 3% piperazine citrate. However, the worms remain alive in pet ether extract at different concentrations even after a long period of exposure. But there was no final recovery in the case of worms treated with chloroform and ethanol extract in contrast to piperazine citrate with which the paralysis was reversible and the worms recovered completely within five hours. The results have been proved that the chloroform extract was moderately active and ethanol extract possesses significant wormicidal activity.