Although only about 8 per cent of pregnancies end prematurely, as much as 75 per cent of perinatal deaths are due to prematurity. Since it is difficult to identify the predisposing factors in individual cases and to prevent the premature onset of labor, it is necessary to try to arrest such labor when it occurs. A theoretical scheme for the mechanism of labor in the human subject is presented. This permits the identification of four possible points of attack: (1) replacement of progesterone to reduce the myometrial sensitivity to oxytocin, (2) administration of beta-mimetic agents to relax the uterus and make it unresponsive to stimuli, (3) administration of ethanol to block oxytocin secretion, and (4) administration of anti-inflammatory drugs to inhibit prostaglandin synthesis. Results obtained with ritodrine, a beta-mimetic agent, and with ethanol are presented as illustration. Ritodrine gave somewhat better results than ethanol, possibly because the treatment was continued after discharge of the patients.