We have studied the use of clonidine combined with low doses of sufentanil and bupivacaine in 45 parturients requiring extradural analgesia for the first stage of labour, in a double-blind, randomized study. We gave 0.0625% bupivacaine 10 ml containing 1:200,000 adrenaline and sufentanil 10 micrograms (1 ml) to which was added 0.9% saline, or clonidine 100 or 150 micrograms (1 ml). We compared the quality (VAS scores) and duration of analgesia, motor block, maternal haemodynamic state (mean arterial pressure and heart rate) and fetal and maternal side effects. Mean duration of anaesthesia was prolonged slightly: 105 (SD 21) min without clonidine, 130 (26) min with clonidine 100 micrograms (P < 0.05 vs control) and 144 (40) min with clonidine 150 micrograms (P < 0.01 vs control, ns vs 100 micrograms). There were no differences in VAS scores, onset times, heart rate, ventilatory frequency, motor block, sedation, pruritus or bradycardia between the groups. Analgesia was associated with a reduction in mean arterial pressure with clonidine. However, these adverse side effects were of minor clinical importance regardless of the extradural clonidine dose, except for a high incidence of fetal heart tracing abnormalities when clonidine 150 micrograms was used. These effects associated with a limited effect on analgesia may curtail the widespread use of clonidine as an adjunct to extradural 0.0625% bupivacaine with sufentanil 10 micrograms during labour.