PIP: A comprehensive review of plants that possess contraceptive or interceptive, abortifacient, ecbolic, oxytocic, or emmenagogue properties is presented. The plants reviewed are those which have a folkloric reputation of contraceptive effects and those which have been tested on laboratory animals for their antifertility effect. The preovulatory, preimplantation, and postimplantation antifertility mechanisms of plant substances affecting the hypothalamus-pituitary, ovary, oviduct, uterus, or vagina are discussed in terms of reproductive differences among laboratory animal species. Lithospermic acid, m-Xylohydroquinone, coronaridine, rutin, and rottlerin are among the few active antifertility principles to be identified in higher plants. Volatile oils, quinine and castor oil, and sparteine have been used as abortifacient agents, but not with consistent success, and often with toxic, if not fetal, side effects.