Prostaglandins appear to have potential value in a wide variety of clinical condition. The name “Prostaglandin” had been given by von Euler in 1935 to a smooth-muscle-stimulating, vaso-depressor, acidic lipid of unknown structure discovered in human seminal plasma and thought to be secreted from the prostate gland. Bergström and Sjöval in 1960 succeeded in isolating two active crystalline compounds from extracts of sheep seminal vesicles. It is now used as a generic term for a family of closely related derivatives of prostanoic acid, which are widely distributed in tissues. Unlike the classical hormones, they are present in most tissues, and can be readily released by simple physiological procedures. Diseases due to inadequate PG synthesis or metabolism have not been identified.