AIM: The aim of this study was to estimate the prognostic information to be gained from ventricular fibrillation in patients with myocardial infarction. METHODS AND RESULTS: We studied 4259 consecutive patients with myocardial infarction admitted to one centre in 1977-1988. Five hundred and twenty-eight (12.4%) of the patients had ventricular fibrillation in hospital. The following risk factors were included in multivariate models to estimate their importance for 30-day and long-term (median 7 year) prognosis: age, gender, ventricular fibrillation, congestive heart failure, pulmonary oedema, cardiogenic shock, other cardiac arrest and atrial fibrillation. We found that the odds ratio for death on days 6.30 was 6.34 (3.55-11.30, 95% confidence limits, P < 0.001) for patients with primary ventricular fibrillation (without heart failure) and 4.06 (2.68-6.14, P < 0.001) for patients with ventricular fibrillation secondary to heart failure compared to patients without ventricular fibrillation. For patients surviving more than 30 days, relative risk of death in those with ventricular fibrillation was 1.11 (95% confidence interval 0.93-1.34, P = 0.26). Logistic regression analysis of relative risk associated with ventricular fibrillation in time intervals, indicated that the importance of ventricular fibrillation for risk of death was exhausted during the initial 60 days after infarction. CONCLUSION: Ventricular fibrillation is associated with an independent increased risk of death within 0-60 days after infarction. After this period, the prognosis in survivors of ventricular fibrillation does not differ significantly from patients without ventricular fibrillation.