Twenty neonates whose mothers had received meperidine (1.0 to 1.5 mg/kg) intravenously within three hours of delivery were studied to determine the effectiveness of naloxone in reversing neonatal respiratory depression. The following measurements were carried out within 20 to 30 minutes after delivery: minute ventilation, end tidal CO2, and ventilatory response to CO2. These determinations were repeated after administration of either placebo or naloxone, 0.01 mg/kg intramuscularly. Minute ventilation and PAco were within a normal range before medication in both groups, but the slope of the CO2 response curve was decreased, indicating mild-to-moderate respiratory depression. After administration of placebo the test results did not change significantly. After administration of naloxone, VE increased significantly (P less than 0.05) and the slope of the CO2 response curve doubled (P less than 0.001). Naloxone effectively reverses narcotic depression of the respiratory center in the newborn infant.