Various steroid hormones, especially D.C.A. and progesterone produce deep anesthesia in rats and mice if injected into the peritoneum whence they can be rapidly absorbed. After recovery from the anesthesia such animals show no ill effects. Partially hepatectomized rats are much more sensitive to the anesthetic effect of the steroids than intact controls. This probably indicates that the liver plays an important rôle in the detoxification of these compounds. Males are less sensitive than females of the same size.