Acute pancreatitis (AP) is a common abdominal disorder with severity varying from mild to fatal disease. Predicting a patient's outcome remains problematic. The aim of this study was to analyze a large consecutive series of patients with severe AP and to identify prognostic factors for hospital mortality. Between 1989 and 1997, a consecutive series of 270 patients with severe AP were included in the study. All patients fulfilled the criteria of Atlanta classification for severe AP. Retrospectively and prospectively collected data included age, gender, etiology, number of previous episodes of pancreatitis, medication history, type of admission, body-mass index (BMI), respiratory failure, renal failure, need for pressor support, and abdominal surgery performed during hospitalization. The overall mortality rate was 24.4%. In univariate survival analysis advanced age, history of continuous medication, patient transferred from other hospital, high BMI, respiratory or renal failure, need for pressor support, and need for abdominal surgery were significant prognostic factors for hospital mortality. In a multivariate stepwise logistic regression analysis, the need of pressor support, renal failure requiring dialysis, advanced age, history of continuous medication and need for abdominal surgery were identified as independent prognostic factors for mortality. A logistic regression analysis of variables available on admission (the first seven above mentioned variables) showed that transferral admission, advanced age, and history of continuous medication were independent prognostic factors for mortality. In patients with severe AP, advanced age, history of continuous medication, and need for dialysis, mechanical ventilator support, and pressor support predict fatal outcome and thus should be taken into account in clinical evaluation.