PIP: After explaining the role of estrogens in normal human physiology with a discussion of fertilization which mentions cytogenetical research, the history of estrogen synthesis, forms of estrogen, and the roles estrogens play in female physiology after birth are discussed. The observation that estrus in an animal was mediated by a chemical agent was made in 1922. In 1927, studies showed that urine of pregnant women contained estrogenic substances, and in 1929, estrone, an oxidation product of estradiol, was isolated from this source. The natural oxidation products of estradiol include, besides estrone, estriol, equilin, and equilenin, these last 3 being very weak estrogens. Conjugated estrogens consist chiefly of sodium estrone sulfate. In 1938, diethylstilbestrol, a nonsteroidal estrogen, was synthesized. A discussion of the estrogens activities when administered orally or parenterally follows; nonsteroidal estrogens are thought to have good oral action as do esterified estrogens. Estrogenic effects on female physiology include secondary sexual characteristics, menstrual cycle, and ovulation. Other estrogen functions mentioned were antidiuretic action, retardation of atherosclerosis, increased calcium deposition in bone, and epiphyseal closure acceleration after initial stimulation. The rationale for and problems with patient package inserts are discussed.