PURPOSE: The exact incidence of myocarditis is unknown, as the diagnosis is frequently delayed or missed. Clinical presentation and disease course are extremely variable, as there may be acute onset with acute coronary syndrome, or cardiogenic shock, or progressive heart failure or arrhythmias. The purpose of this study was to identify prognostic factors on magnetic resonance imaging (MRI) performed in patients with bioptically proven myocarditis at presentation and after 6 months. MATERIALS AND METHODS: Fifty-six consecutive patients with different presentations of myocarditis (20 with acute coronary syndrome, 20 with heart failure, 16 with arrhythmias) were enrolled. All patients underwent B-mode echocardiography (echo) and tissue Doppler imaging, coronarography, ventriculography, endomyocardial biopsy and contrast-enhanced MRI examination, as well as clinical and echo follow-up at 6 months. RESULTS: At 6-month follow-up, patients were divided in two groups according to values of end-systolic volume and ejection fraction: patients with negative remodelling and those with positive remodelling. Late enhancement was found to be an independent predictor of negative remodelling. CONCLUSIONS: Contrast-enhanced MRI is useful both in the diagnosis and as a prognostic indicator in the clinical suspicion of myocarditis.