To determine whether a standardized dose of esmolol can effectively attenuate the cardiovascular response to electroconvulsive therapy (ECT), 17 ASA physical status I-II patients were studied in a randomized within-patient, crossover design. Each patient received "no esmolol" during one ECT and three to five days later crossed over to the alternative treatment receiving an esmolol 80 mg bolus followed by 24 mg.min-1 infusion two minutes prior to induction of anaesthesia and continued for five minutes after induction. Esmolol blunted the maximum increases in heart rate (HR) by 26 per cent, mean arterial pressure (MAP) by 14 per cent, and rate pressure product by 37 per cent with significant differences (P less than 0.05) noted at one, two, three and four minutes after ECT (minutes five, six, seven, and eight of the esmolol infusion). There was no significant difference in seizure duration between the two groups and no adverse reactions occurred.