The effects of two different concentrations of epidural levobupivacaine were compared when used to provide analgesia for labour. Primiparous women in spontaneous uncomplicated labour were enrolled in a prospective, randomised and partially double-blinded study. The study solutions were either 0.568 mg x ml(-1) levobupivacaine (low concentration group) or 1.136 mg x ml(-1) levobupivacaine (high concentration group), with sufentanil 0.45 microg x ml(-1) added to both solutions. Epidural analgesia was initiated with 20 ml of the study solution, followed by a standardised algorithm of top-up bolus injections. Epidural analgesia was then continued by self-administered boluses of 5-ml plus a continuous infusion of 5 ml x h(-1). Analgesia was found to be more efficacious in the high-concentration group. The dose of levobupivacaine administered was higher and sometimes overstepping recommended limits in the high concentration group, but with no observed increase in side-effects. The choice between these two concentrations may still be made according to the patient's and the practitioner's preferences. The effects of an intermediate concentration should be studied in the future.