PIP: Literature on the phytochemical study of plant estrogens is reviewed. The coumestans reportedly have a greater degree of estrogenic activity than the isoflavones. Diethylstilbestrol is the prototype of the synthetic silbene derivatives. Of the natural stilbenes, only rhaponticin possesses estrogenic activity, though this is not firmly established. 6, 4'-dihydroxyflavone has also been reported to have estrogenic activity. Coumestrol and genistein have been shown to compete with 17beta-estradiol for binding sites in the uterus of young rabbits. Vinblastine, demecolene, and podophyllotoxin posses known cyto toxic, antifertility properties. Naturally occurring steroid estrogens, estrogenic isoflavins, coumestans, plants with reported estrogenic activity, and cytotoxic agents with antifertility properties are listed along with their plant sources.