We have examined the ability of lemakalim to correct bupivacaine-induced cardiac electrophysiological impairment in an experimental electrophysiological model in closed-chest dogs. Two groups (n = 6) of pentobarbitone-anaesthetized dogs were given atropine 0.2 mg kg-1 i.v., and bupivacine 4 mg kg-1 i.v. over 10 s. Group 2 received also lemakalim 0.03 mg kg-1 i.v. Bupivacaine induced bradycardia, prolonged PR and His-ventricle (HV) intervals, QRS duration, QTc and JTc intervals, decreased left ventricular (LV) dP/dt max and increased LV end-diastolic pressure. Lemakalim reversed bupivacaine-induced PR, HV, QRS, QTc and JTc prolongation, and did not worsen bupivacaine-induced bradycardia and haemodynamic depression. We conclude that lemakalim can antagonize the main deleterious electrophysiological effects induced by a large dose of bupivacaine in anaesthetized dogs.