The announcement in 1949, by Hench at the Mayo Clinic, that cortisone had a dramatic beneficial effect on bed-ridden patients suffering from rheumatoid arthritis ushered in the cortisone era. This medical landmark was made possible by the prior steroid research of distinguished chemists and biologists in several countries. The first partial synthesis of cortisone by Sarett was the culmination of a worldwide chemical effort. This work ultimately enabled the process research department at Merck, under the direction of Max Tishler, to perform the 37-step conversion of deoxycholic acid to cortisone on a scale that made the initial clinical trials possible. In spite of the enormity of the project, and the fact that neither of two closely related analogs of cortisone had shown any interesting biological activity. Merck elected to embark on this synthetically challenging project. The clinical results reported in 1949, combined with the complexity of the partial synthesis, stimulated highly innovative research to discover new routes to cortisone and to cortisol, the active hormone. This research, particularly in the pharmaceutical industry in the United States, Mexico, and Europe, demonstrated, among other things, the value of microbial transformations in synthetic sequences. The recognition that the chronic administration of cortisol produces several unexpected side effects stimulated an intensive effort in many countries to discover an analog with an improved therapeutic index. This led to more novel chemistry and many analogs were discovered that proved to be more potent than cortisol. Prednisolone, discovered at the Schering Corporation, was the first compound that combined a high level of anti-inflammatory activity with reduced salt retention. Derek Barton contributed greatly to steroid research during the 1950s by applying creative structural thinking to systematize a host of seemingly unrelated chemical and biological observations. The cortisone era had a profound impact on drug discovery also, since it led to the logical application of steric and electronic concepts to medicinal chemistry. Last, but not least, the cortisone era taught medicinal chemists many important lessons about drug-receptor interactions.