Epidural anaesthesia with local anaesthetics has become a standard method of pain relief during labour. In recent years, spinal opiates, alone and in combination with local anaesthetics, have also been tried with varying degrees of success. Buprenorphine, a potent lipophilic opiate with long duration of action, has been used in several trials for caesarean section [3, 4, 6], but not yet in spontaneous labour. The aim of the present investigation was to evaluate epidural anaesthesia with bupivacaine alone and with bupivacaine+buprenorphine in comparison with no anaesthetic treatment in control parturients. METHODS. A total of 80 healthy women during labour at full term (age 18-38 years, weight 54-107 kg) were studied to evaluate the influence of 0.3 mg buprenorphine (group BB) vs placebo (group B) added to an initial dose of 15 ml plain bupivacaine 0.33% for lumbar catheter epidural anaesthesia. Plain bupivacaine 0.25% (10 ml) without any opiate admixture was used for reinjections. The control group was made up of 48 untreated parturients. After every injection, blood pressure, heart rate and respiratory rate were measured repeatedly, as were time intervals between injections, extent of blockade, duration of labour, actual and retrospective visual analogue pain score, and side effects such as pruritus, shivering or nausea and emesis. Maternal capillary blood gases were analysed three times during labour, and Apgar scores and venous and arterial umbilical blood gas analyses were obtained immediately after delivery. RESULTS. Admixture of buprenorphine 0.3 mg significantly increased the time interval between the first and second epidural doses (B: 162 +/- 47 vs BB: 224 +/- 64 min; mean, SD; Table 2) and significantly reduced the incidence of shivering (Table 9). The incidence of instrumental delivery was comparable in all groups (bupivacaine 32.5%, bupivacaine+buprenorphine 27.5%, control 21%; n.s.). No clinically relevant differences were observed between the epidural patients in onset and duration of the block (Fig. 1), analgesic efficacy (Fig. 2), duration of spontaneous labour (BB: 8.6 +/- 3.1 h, B: 8.5 +/- 2.9 h; n.s.) and vital functions of mothers and newborns. Although some statistically significant differences between the three groups were found in some parameters of the blood gas analyses (Table 7), the clinical condition of the newborns was always acceptable; Apgar scores were not significantly different. DISCUSSION AND CONCLUSIONS. The addition of buprenorphine to bupivacaine resulted in some advantages to the mother (reduced incidence of shivering) and the anaesthetist (time lapse before first reinjection was necessary) without jeopardizing the situation of the baby. Compared with untreated control parturients, retrospective pain scores during epidural anaesthesia with bupivacaine (with or without buprenorphine) were significantly lower. No clinically relevant disadvantages of epidural anaesthesia were observed. More studies are required to evaluate whether buprenorphine admixture allows a dose reduction of bupivacaine and could then claim clearer advantages than were found in the present investigation.