This paper gives in narrative style those phases of the corpus luteum story in which the author was an active participant. The first part deals with the exciting days at the University of Rochester where the pure hormone was isolated in 1933 and where many of the effects of the hormone on target tissues were elucidated. The origin of the name, progesterone, is given as a fine example of international cooperation in the selection of a name which has been universally accepted. The accidental discovery of the ‘Blue Color Test’ for DHIA and the development of the Allen-Correction at Washington University in St. Louis are recounted as sideline adventures in science. The final part recounts the steps, extending over a period of 40 years, which have clarified the role of the human corpus luteum in pregnancy.