AIMS: The purpose of this study was to evaluate the influence of left ventricular systolic function on the survival in a large consecutive cohort of patients hospitalized with congestive heart failure and to determine how left ventricular systolic function interacts with co-morbid conditions in terms of prognosis. METHODS AND RESULTS: Analysis of survival data from 5491 patients admitted for new or worsening heart failure to 34 departments of cardiology or internal medicine in Denmark from 1993-1996 was carried out. A standardized echocardiogram was available for 95% of the patients, and left ventricular systolic function was estimated using wall motion index score. Follow-up time was 5-8 years. Patients with preserved systolic function were older, more frequently female, and had less evidence of ischemia than patients with systolic dysfunction. After 1 year, 24% of the patients had died. Low wall motion index was a potent independent predictor of death (risk ratio for one unit increase, 0.60 (0.56-0.64)), and was of greater prognostic significance in younger patients and patients with a history of myocardial ischemia. However, even in patients with preserved systolic function, mortality was high (1 year mortality, 19%). CONCLUSION: In hospitalized heart failure patients, particularly in younger patients with ischemic heart disease, mortality risk is inversely related to left ventricular systolic function.