Prostaglandins may act at several sites in the reproductive system. They may stimulate pituitary gonadotrophin secretion by mechanisms not yet clearly defined. These compounds probably play a direct role in the ovulatory process and may be the uterine luteolysin. Prostaglandins are best known for their stimulatory action on the uterus, and clinical experimentation has centered on their effectiveness as abortifacients. While prostaglandins have not been shown to be superior to oxytocin (Syntocinon) in the induction of term labor, and studies using these compounds as "contraceptives" have thus far been disappointing, they do appear to offer an effective and superior method of inducing midtrimester abortion.