Infants born to mothers receiving 100 mg of pethidine during labor, were randomly given either 100 micrograms of naloxone (n = 14) or 0.25 ml 0.9% NaCl (n = 13) one hour post partum. Infant behavior was assessed with the Brazelton Neonatal Behavioral Assessment Scale (BNBAS) and the Broussard Neonatal Perception Inventory (NPI). No differences in cluster scores on the BNBAS were found between the two groups. Both groups improved scores over time in 4 out of 7 clusters. On the NPI, mothers assessed naloxone infants as having less optimal behavior than did the control mothers. The results of this study on the effects of naloxone on infant behavior and maternal perception of newborn behavior do not warrant administration of naloxone after maternal analgesia with pethidine in the absence of clinical evidence of respiratory depression in the newborn.