Although sulfur tetrafluoride is a remarkably versatile agent for selectively introducing fluorine atoms into organic compounds, its existence was doubted as late as 1950. A colorless gas boiling at -38o C, sulfur tetrafluoride was probably first made by treatment of sulfur with uranium hexafluoride and subsequently by the reaction of sulfur with cobalt(III) fluoride. Both products were of questionable purity. In 1950 sulfur tetrafluoride was unequivocally synthesized by electrical decomposition of trifluormethylsulfur pentafluoride. It was not until 1955 that gram amounts were prepared and thus making sulfur tetrafluoride a viable compound. This led the way for the discovery of its remarkable fluorinating ability. The ability of sulfur tetrafluoride to replace carbonyl oxygen selectively is probably the most useful synthetic application.