Congestive heart failure (CHF) is known to be highly fatal, but to better assess efficacy of therapeutic interventions a greater understanding of its course is required. Previous studies of survival are limited by heterogeneity of patient populations and diverse criteria for diagnosing CHF. We followed up 182 patients with chronic left ventricular failure who were symptomatic despite therapy. The length of the follow-up period averaged 12 ± 10 (mean ± standard deviation [SD]) months (range 1 to 41). The cause of CHF was coronary artery disease in 95 patients and idiopathic dilated cardiomyopathy in 87. A total of 88 deaths occurred, of which 40 (45%) were sudden; the incidence of sudden death was similar in patients with coronary artery disease and idiopathic dilated cardiomyopathy. The overall mortality rate was 34% at 1 year, 59% at 2 years, and 76% at 3 years. The mortality rate in patients with coronary artery disease was 46 and 69% at 1 and 2 years, compared with 23 and 48% at 1 and 2 years in those with idiopathic dilated cardiomyopathy (p <0.01). Comparison of all survivors and nonsurvivors showed no difference in age or duration of symptoms at entry. Clinical class was significantly worse in nonsurvivors. Nonsurvivors had higher left ventricular filling pressure (29 ± 7 versus 24 ± 9 mm Hg) and systemic vascular resistance (25 ± 10 versus 21 ± 8 units) (both p <0.01); they also had lower mean arterial pressure (87 ± 13 versus 94 ± 13 mm Hg), cardiac index (2.0 ± 0.7 versus 2.5 ± 0.8 liters/min/m2), and stroke work (35 ± 19 versus 56 ± 33 g-m) than did the survivors (all p <0.001). However, only left ventricular filling pressure was correlated with length of survival (r = -0.31, p <0.01). Thus, 3-year mortality is very high in patients with severe chronic left ventricular failure. The prognosis is poorer in patients with CHF due to coronary artery disease and, as expected, in those with worse symptoms and hemodynamic abnormalities.