Résumé : Background: Determination of severity of acute pancreatitis is important to determine prognosis. Aims: (1) the staging of acute pancreatitis by computed tomography and magnetic resonance imaging, (2) the correlation of computed tomography and magnetic resonance severity indices and 3) the correlation of magnetic resonance severity index with C-reactive protein, Ranson score, duration of hospitalization and clinical outcome. Patients: Thirty-five patients (median age: 64 (27-89)) were studied. Twenty-two patients had biliary acute pancreatitis. Methods: The following examinations were conducted: (1) computed tomography 48 h, 7 and 30 days after admission, (2) magnetic resonance imaging 7 and 30 days after admission, (3) C-reactive protein and 4) Ranson score. Clinical outcome was determined on a scale 0-3 (0: remission, 1: local complications, 2: systemic complications, 3: death). Results: Six of 35 patients (17%) had necrotizing acute pancreatitis. Fifteen of 35 patients (43%) had severe acute pancreatitis according to Ranson criteria. A significant correlation was noted between magnetic resonance severity index and C-reactive protein (r = 0.419, p < 0.005), Ranson score (r = 0.431, p < 0.05), duration of hospitalization (r = 0.497, p < 0.01) and clinical outcome (r = 0.420, p < 0.05). Comparison of the imaging methods showed a significant correlation between magnetic resonance severity index and computed tomography severity index (r = 0.887, p < 0.01). Conclusion: Magnetic resonance imaging is of comparable diagnostic and prognostic value with computed tomography in the staging of acute pancreatitis. © 2007 Editrice Gastroenterologica Italiana S.r.l.