Abstract
In the white rat, administration of estrogens and androgens produce regression and atrophy of the tumors of intrasplenic ovarian grafts and this effect represents a specific action of the hormones. Neither hormone influences the development of cystic ovarian grafts. When tumor degeneration does occur, the cessation of hormone administration is not followed by regeneration of the tumor. It is postulated that tumor destruction is caused by the depressing effect of the hormones on the gonadotropic function of the hypophysis.