Accelerated idioventricular rhythm has been used as a marker for coronary reperfusion. The incidence of accelerated idioventricular rhythm and ventricular tachycardia was evaluated in 52 consecutive patients undergoing thrombolysis with intracoronary streptokinase during acute myocardial infarction. Complete 12-hour Holter recordings during and after intracoronary streptokinase were obtained in 39 patients. Reperfusion was documented in 17 patients (44%), no reperfusion in 14 (36%), and subtotal occlusion in eight (20%). Accelerated idioventricular rhythm occurred in 83%, 57%, and 63% of patients by group, respectively (p greater than 0.05). Ventricular tachycardia occurred in 100%, 71%, and 100% of patients by group, respectively (p less than 0.05). These data demonstrate that accelerated idioventricular rhythm is not specific for reperfusion and cannot be used as a marker for this event, and that ventricular tachycardia is more common with reperfusion and subtotal occlusion.