A retrospective review was done to determine the efficacy and hemodynamic effects of slow intravenous amiodarone administration on invasively monitored patients with acute onset of atrial fibrillation or atrial flutter and left ventricular ejection fractions < 15%. Eight patients met predefined inclusion criteria. All received 300 mg amiodarone intravenously over 1 hour. Seven reverted to sinus rhythm within 1 hour, with return of most hemodynamic variables to baseline. Before reversion, each patient experienced a beneficial slowing of heart rate (mean, 28%) resulting in significant improvement of stroke volume index (mean, 49%) and left ventricular stroke work index (mean, 61%). No patient had hemodynamic deterioration attributable to amiodarone infusion. Slow intravenous infusion of amiodarone appears to be an effective and hemodynamically well-tolerated therapy for atrial fibrillation and atrial flutter in critically ill patients with marked depression of left ventricular systolic function.