It has not been determined previously whether patients with severe chronic congestive heart failure differ in demographic characteristics with respect to left ventricular systolic dysfunction (LVD). In patients with severe chronic congestive heart failure in NYHA IV, an optional protocol in the CONSENSUS-I trial was designed to ascertain whether there were any differences in patient characteristics regarding the degree of LVD defined as left ventricular fractional shortening (FS). A subgroup of 54 patients from the CONSENSUS-I trial were evaluated with M-mode echocardiography. Patients with FS above median (14%) were older (74 ± 7 vs. 68 ± 7, p < 0.0l), more often female (48 vs. 15%, p < 0.05) and had lower heart rates (77 ± 15 vs. 95 ± 17, p < 0.01). Analysis of the 2-year follow-up from the end of the trial was also performed. In the placebo group, patients with FS > 14% had significantly better prognosis than patients with FS < 14%. In the enalapril-treated group no such difference in survival was seen. The difference between the original treatment groups remained, despite the fact that treatment with enalapril was then made available to all surviving patients. In conclusion, patients with advanced chronic congestive heart failure and less severe LVD have different demographic characteristics than patients with more severe LVD. In the placebo group, but not in the enalapril group, prognosis was better in patients with less severe LVD.