Vasectomy is a useful procedure for the prevention of pregnancy when this is permanently unwise because of hereditary characteristics which should not be transmitted or physical conditions which make parenthood dangerous to life or health or when a couple has had all the children for whom they can adequately care. Its use is limited by apprehension on the part of the average person that a handicap in sexual life may result. Since the operation consists only of the closure of the two small ducts through which the spermatozoa pass and does not require the removal of organ or gland, sexual change seems improbable. Such a change is, however, so important that careful review is worth adding to presumption. PREVIOUS INVESTIGATIONS Some follow-up studies of vasectomized patients are on record. To determine the results of vasectomy, Popenoe1 arranged for letters to be sent by the superintendents of California state hospitals