The antiarrhythmic action of disopyramide (1.5 mg/Kg) administered i.v. as a bolus was assessed in 30 patients with ischemic heart disease and different arrhythmias. In 75% of supraventricular parossistic tachycardia and in 75% of parossistic atrial fibrillation, arrhythmia was interrupted within few minutes from drug injection; in 90% with premature ventricular contractions (PVC) and in 100% of ventricular tachycardia, disopyramide was capable to interrupt the arrhythmias. The hemodynamic effects of the same dose of disopyramide were evaluated in other 17 patients, 9 of which in I-II class NYHA and 8 in III-IV class. We used STI's as parameters of cardiac performance. In all patients following the injection of disopyramide, a significant increase of PEP, ICT and PEP/LVET ratio and a significant decrease of LVETc were observed. Thus, the disopyramide impaired cardiac performance and its effect appeared more evident in patients in III-IV class NYHA. In conclusion, disopyramide showed to be effective in interrupting different arrhythmias; however, its depressant action on cardiac performance suggests that caution should be used in patients with severely impaired myocardial function.