The association of bupivacaine and fentanyl appeared as the best method of inducing satisfactory obstetrical analgesia. But the various techniques of drug administration had to be detailed; this justified the present work, a single-blind controlled trial performed on 159 primipara women at term (except one of them), randomized in four groups, after informed consent. In each group, the number of patients, the age and the degree of uterine dilatation at the beginning of the epidural anaesthesia were comparable. Epidural anaesthesia aimed to improve the maternal comfort during labour. After a first epidural injection of 10 ml, several other injections of 6 ml were carried out according to four different protocols (I, II, III, IV), with different concentrations of fentanyl (respectively 0, 0.05, 0.1 and 0.15 mg). The mean total dosages of fentanyl were statistically higher in the protocols III and IV. The foetal cardiac rhythm and uterine contractions were monitored continuously as well as maternal blood pressure and heart beats during labour. The following parameters were assessed : contraction pain intensity (five point scale), the onset of analgesia, the duration of analgesia, the length of labour, the interval between the first drug injection and subsequent injections, the type of delivery. In the newborn, Apgar score was assessed at 1, 5 and 10 min after delivery. The degree of analgesia was statistically improved in the groups reciving fentanyl, without any differences between them. On the other hand, the length of labour was shorter with protocol II (lowest concentration of fentanyl). The highest doses of fentanyl (protocols III and IV) were associated with an increase in the number of forceps and caesarean sections; moreover, uterine hypertonia occurred more frequently in protocols III and IV, especially under oxytocin infusion. In the four groups, Apgar scores were at 10, 10 min after delivery (except for a dead twin new-born). No respiratory depression was noted in either the women or the children during the 6 h following delivery. Localized pruritus induced by fentanyl appeared in 20 % of the women. No vascular collapse occurred. Statisfactory analgesia was obtained with 0.05 mg of fentanyl associated with 9 ml of bupivacaine at 0.25 %, suggesting a total occupation of the opiate receptors involved in the contraction pain. Before concluding on the validity of this technique, a precise study of the consequences of the administration of drug mixtures on the newborn has to be analysed.