The authors describe the challenging case of a 46-year-old patient who presented with a 2-week history of exertional dyspnea, paroxysmal nocturnal dyspnea, and orthopnea. He was found to have left ventricular failure and atrial fibrillation with a rapid ventricular rate. Initial work-up revealed dilated cardiomyopathy with marked left ventricular dysfunction, without any obvious cause. He received standard medical therapy for left ventricular dysfunction and his symptoms improved. Electrical cardioversion to sinus rhythm and maintenance resulted in complete recovery of left ventricular function within 6 months. (c)2001 CHF, Inc.