This randomized investigation compared the efficacy of the conventional narcotic, meperidine, and a more potent and short-acting analgesic, fentanyl, during labor. One hundred five women with uncomplicated term pregnancies in active labor were randomly assigned to receive either intravenous fentanyl (50-100 micrograms every hour) or meperidine (25-50 mg every 2-3 hours) in a non-blinded manner. The analgesics were rated equivalent in efficacy. Maternal nausea, vomiting, and prolonged sedation occurred more frequently in the meperidine group. Naloxone use was significantly less in fentanyl- than in meperidine-exposed infants (one of 49 versus seven of 56; P less than .05). Neuroadaptive testing at approximately 2 hours and 24 hours postnatally revealed similar averaged scores in the two groups. Using the described intravenous dosing schedule, fentanyl was preferable to meperidine during labor because there was no prolonged maternal sedation or vomiting necessitating therapy and the requirement for neonatal naloxone was reduced.