Bupivacaine is the most widely local anaesthesic used in obstetric for epidural analgesia. Nineteen women, mean-age 26.9 +/- 5.3 years, who underwent epidural analgesia during labour, were included in our study. All parturients received a first injection with 21.8 +/- 2.5 mg of 0.25 % bupivacaine. The following administrations were given on request; a 0.25 % concentration was used when cervix uteri was supple and a 0.375 % concentration when it was tonic. Blood samples were collected 5 min after the first injection and then, every 30 min until the delivery. At the delivery two other blood samples were collected: one from the infant ombilical vein and the other, from the arm vein of the mother. Bupivacaine was assayed by high pressure liquid chromatography. Serum data were analysed for each patient using a single compartment open model.Bupivacaine was rapidly detected in serum and the maximal concentration was reached between 5 and 35 min. Pharmacokinetic parameters were estimated in 17 women after the first injection: 87 +/- 35 min for elimination half-life, 60 +/- 19 l for apparent volume of distribution and 0.5 +/- 0.3 ml/min for plasmatic clearance. For a mean total duration of labour and total dose administred of respectively 222 +/- 115 min and 57.1 +/- 28.7 mg, the mean value of the foeto-maternal ratio was 0.29 +/- 0.10. The infant maximal serum concentration was 0.26 μg/ml. No side effect was spontaneously reported by the parturients and all infants have got an Apgar score of 10, five minutes after the delivery.We confirm the fast systemic absorption and rapid elimination of bupivacaine which can be used without risk of acute and cumulative toxicity both in mother and child, even when it is used in a 0.375 % concentration.