Improvement in the early phase of myocardial infarction (MI) is associated with a higher rate of late complications, including late-onset heart failure (LHF). The factors predicting LHF are not well understood. Our aims were to identify the factors predicting LHF and to determine the survival rate in these patients. The GISSI-Prevenzione trial involved 11,323 low-risk patients (NYHA class < or = II) who had had a recent MI (< 3 months). It was a multicenter, open-label, clinical trial of the efficacy of treatment with polyunsaturated fatty acids, vitamin E, both, or neither. Patients with heart failure at baseline and those whose ejection fraction was unknown (n = 2908) were excluded from the present analysis. Late-onset heart failure was defined prospectively as hospital admission due to heart failure. A Cox regression model adjusted for major covariates was used for risk analysis. The study included 8415 patients. During 3.5 years of follow-up, 192 (2.3%) developed LHF. The risk of LHF could be predicted from readily available parameters: age (per year; RR=1.07; 95% CI, 1.05-1.09), ejection fraction (per 1% increment; RR=0.96; 95% CI, 0.94-0.97), heart rate (> or = 74 beats/min; RR=1.62; 95% CI, 1.21-2.16), white blood cell count (> or = 8900 per ml; RR=1.42; 95% CI, 1.05-1.94), diabetes (RR=1.62; 95% CI, 1.17-2.24), hypertension (RR=1.76; 95% CI, 1.33-2.34), peripheral artery disease (RR=2.11; 95% CI, 1.32-3.37), and reinfarction (RR=2.09; 95% CI, 1.28-3.39). LHF was associated with poor survival: (RR=2.34; 95% CI, 1.63-3.36). The risk of LHF in post-MI patients can be predicted from readily available parameters. LHF was associated with a poor prognosis.