This was a prospective, non-randomized, multi-centre study of rocuronium (Org 9426) in 40 elective Caesarean section patients at full term without fetal distress. Anaesthesia was induced with thiopentone 4–6 mg kg−1 i.v. and rocuronium 0.6 mg kg−1 and maintained with isoflurane and nitrous oxide in oxygen. Monitors included ECG, arterial pressure, pulse oximeter and train-of-four (TOF) produced by ulnar nerve stimulation. In all patients, full neuromuscular block at the hand indicating the maximum effect of rocuronium (T1 = 0) occurred at a mean time of 98.1 (SE 9.4) s. However, after 79.3 (2.9) s, excellent to good intubating conditions were achieved in 90% of patients. Injection to delivery time was 12.7 (0.9) min and the surgical procedure tasted 53.1 (3.5) min. After administration of rocuronium, T2 appeared after 32.7 (1.8) min (indicating duration of effect). At the end of the surgical procedure in 39 patients, glycopyrronium 0.2 mg and neostigmine 1 mg were given every 5 min to antagonize residual neuromuscular effect. The mean dose of neostigmine required was 1.54 (0.1) mg. Rocuronium had no clinically significant effect on maternal heart rate or arterial pressure. After administration of thiopentone and rocuronium in two patients, temporary erythema occurred, one along the site of injection and the other on the chest wall. Rocuronium had no untoward effects on the neonates, evaluated by 1- and 5-min Apgar scores, time to sustained respiration, total and muscular neuroadaptive capacity scores, acid-base status and blood-gas tensions in umbilical arterial and venous blood. At delivery in 32 patients, concentrations of rocuronium in maternal venous (MV) and umbilical venous (UV) plasma were 2412 (180) ng ml−1 and 389.6 (27.8) ng ml−1, respectively (UV/MV ratio 0.16). In 12 patients, the mean concentration of rocuronium in umbilical arterial (UA) plasma was 271.2 (34.7) ng ml−1 with a UA/UV ratio of 0.62. 17-Desacetylrocuronium (Org 9943), the main metabolite of rocuronium, was below the sensitivity level (25 ng ml−1) in umbilical venous and arterial plasma; the maternal venous plasma concentration was 178 (31) ng ml−1.