A prospective, randomised, double-blind study was conducted to compare the efficacy of two doses of levobupivacaine combined with sufentanil for continuous epidural infusion following thoractomy. A total of 72 patients undergoing lobectomy or pneumonectomy were enrolled. An epidural catheter was inserted between the levels of T4 and T6 before induction of anaesthesia and a loading dose of levobupivacaine and sufentanil was administered. At the end of surgery an epidural infusion was commenced at 5 mlxh(-1) and continued for 48 h. Patients were randomly allocated to receive either levobupivacaine 0.125% (group A) or 0.0625% (group B) and all patients also received sufentanil (1 microgxml(-1)). Visual analogue pain scores after coughing (VASi) were always higher in group B (p < 0.05); VAS pain scores at rest were higher for the first 4 h and at 16 and 28 h in group B (p < 0.05). Total morphine consumption and requests number was lower in group A (p < 0.05). Better pain relief was achieved using epidural 0.125% levobupivacaine.