The prostaglandins are lipid-soluble C20-carboxylic acids containing a five-membered ring, several oxygen function, and at least one double bond. They are found in animal organisms where they stimulate, inter alia, the smooth muscle. In the last decade more has been learned about the occurrence, biosynthesis, metabolism and pharmacological properties of the prostaglandins. Analytical methods for their determination, and syntheses for the naturally occurring prostglandins and their synthetic analogs have been developed. In this report, an attempt is made to show why new knowledge has dramatically stimulated pharmaceutical research in this field.