While the number of deaths from coronary artery and cerebrovascular disease is clearly decreasing in the U.S., the prevalence of congestive heart failure (CHF) seems to be increasing. Many studies have found that more than half of the CHF-related deaths are sudden, and presumably are due to ventricular arrhythmias. Knowledge of the pathophysiology of arrhythmias in the patient with CHF is limited, but left ventricular mechanical abnormalities, diuretic-induced hypokalemia, hypomagnesemia and inotropic therapy may play a role. The prevalence of couplets, multiformed ventricular premature complexes or both is very high, averaging 87% in 8 different studies. The prevalence of nonsustained ventricular tachycardia, determined by ambulatory electrocardiographic recordings, is also quite high; it is approximately 54% in these same studies. Although still unclear, some data now suggest that ventricular arrhythmias may independently influence prognosis in patients with CHF. Future research is obviously necessary to evaluate the influence of antiarrhythmic therapy on survival. However, preliminary findings appear to indicate that treatment may not affect long-term survival in these patients.