The aim of the study was the early identification of patients with acute pancreatitis who subsequently developed critical complications. All patients admitted to a surgical ward for acute pancreatitis were recruited into the study. The severity of acute pancreatitis was assessed using Ranson and Balthazar scores. Patients transferred to the intensive care unit (Group A) were matched with patients with the same scores who did not require intensive care treatment (Group B). Several clinical and biochemical variables were compared between the two groups. A total of 221 patients were recruited (110 m, 121 f; mean age: 60.6 years; range: 17-94 years). Group A included 13 patients (7 m, 6 f; mean age: 59.6 +/- 13.5 years; range: 35-76), whereas Group B included 27 patients (11 m, 16 f; mean age 60.8 +/- 5.5 years; range: 44-93). Only glycaemia, pH, white cell count and body mass index differed between the two groups. The mortality rates were 31% in Group A and 7.4% in Group B, respectively (P<0.005) In the logistic regression analysis, only body mass index continued to show a significant difference. In this population of patients with acute pancreatitis, only body mass index proved capable of identifying patients at risk of critical complications.