Morphinic drugs added to epidural local anesthetic during labour enhance analgesia and obstetrical conditions. Fentanyl, 1 microgram/kg-1, is safe for the newborn. Alfentanil is of faster and shorter duration and its pharmacokinetics suggests less accumulation than fentanyl. The aim of this study is to compare Alfentanil versus Fentanyl when added to an epidural continuous bupivacaine 0.125% infusion. Two groups of parturients are constituted: group A 10 micrograms/kg alfentanil, group F 1 microgram/kg fentanyl. Pain is assessed with a 0 to 10 points scale. There are no differences between the two groups for age, weight, parity, term, initial cervical dilatation and new born weight. Analgesia begins quickly in the two groups, and is more pronounced in the group A (than in the group F (p less than 0.005). Analgesia is maintained for the whole dilatation course. Pain scores increase during expulsion but are significantly lower than the initial scores. No difference is noted as regards analgesia supplementation. Obstetrical data: labour duration, oxytocin dosage, expulsion strength, instrumental extraction rate and uterin evacuation are similar in the 2 groups. No cesarean section is observed. Neonatal status, established according to Apgar scores and then Amiel Tison neurological scales (0 to 30) respectively at 30 to 120 minutes are in the same favorable ranges: Apgar score is in all cases more than 9. The neurological score is 24 (group A) and 22.9 (group F) at 30 minutes and increases significantly at 120 minutes in the 2 groups (27 in the two groups).(ABSTRACT TRUNCATED AT 250 WORDS)