Twelve documented cases of true hermaphroditism have been studied since 1965; there was histological evidence of both ovarian and testicular tissue in all cases. The clinical, anatomical, and therapeutic procedures are reviewed with special emphasis on gonadal morphology, histology, and function. Seven patients were reared as females, 5 as males; 6 are now postpubertal and 3 are more than 30 years old. Five underwent bilateral castration; in seven cases, only the discordant gonadal tissue has been removed so that these patients may have endogenous gonadal secretion in keeping with their sex of rearing.