It has been reported previously that Pisum Sativum (the common field pea) acts as a contraceptive. A series of animal experiments on white rats were performed and the results published (Sanyal, 1950–55) demonstrating its contraceptive effect due to the inhibition of the peripheral action of progesterone and consequent prevention of nidation of a fertilized ovum. Subsequently the active substance was located in the oil of the seeds, isolated in the pure state and its chemical nature determined. The synthesis of the active principle was also effected. The results of animal experiment on white rats with the synthetic active principle, m-xylohydroquinone, corroborated the previous experimental results. Further spectrophotometric studies in vitro as well, demonstrated that m-xylohydroquinone alone, and not its isomers, can interfere with progesterone. But in the language of Professor Swyer of the University College Hospital, London (England), to argue from rats to human beings is rather a risky procedure.