The authors describe the case of an epileptic patient in chronic therapy with carbamazepine, and with plasma concentration of the drug in therapeutical range, who suffers from persistent sinus tachycardia. At the present time the observations available in the literature on cardiac toxicity of carbamazepina concern the appearance of sinus tachycardia as consequence of overdose and of blocks of conduction in elderly with carbamazepine in therapeutical range.