To determine whether Lamaze childbirth preparation is harmless, harmful, or beneficial, 500 consecutive Lamaze-prepared patients were compared to 500 hand-picked controls, matched for age, race, parity, and educational level. Lamaze preparation was found to have a significant beneficial effect in almost every obstetric preformance category. The Lamaze-oriented patients had one-fourth the number of cesarean sections and one-fifth the amount of fetal distress (P < .005). Postpartum infection, measured both by maternal febrile morbidity and by the incidence of antibiotic use, was one-third that of the controls (P < .005). Similarly, the "prepared" patients had fewer perineal lacerations and those that occurred were not as serious as those in the control patients (P < .005). The control patients had three times as many cases of toxemia of pregnancy (P < .005) and twice as many of prematurity (P < .05).