We evaluated the effect of the antipsychotic olanzapine on electrical activity of rat hearts under conditions of ischemic- reperfusion injury. We focused on the prolongation of the corrected QT interval as a risk factor for the incidence of different types of dysrhythmias. Pretreatment with olanzapine showed prolongation of the corrected QT interval as well as increased incidence of dysrhythmias in following order: ventricular premature beats > bigeminies > trigeminies > salvos. We also observed an increase in the frequency of episodes of ventricular tachycardia of about 64% and the average duration of ventricular tachycardia was more than doubled under the conditions of the ischemic-reperfusion injury.