This paper reports the results of a study of a series of 200 gonad failures, a considerable proportion of whom were [male] and [female] castrates. Following the practice of the earlier papers, the 1st part is devoted to a consideration of the laboratory studies, the 2nd to the clinical evidences, while the 3rd gives the case protocols of a number of patients presenting special features. Among these was a group of genital anomalies, homosexuality , a group of castrates [male] and [female] gonad failures following mumps, together with sterility, psychosis, and deafness. Some studies of normal pregnancy were reported to illustrate the close parallelism between the pregnant woman and the woman with ovarian failure. In addition cases of developmental arrest, obesity, and functional failure are discussed.