['APACHE II is a multifactorial scoring system for predicting severity in acute pancreatitis (AP). Organ failure (OF) has been correlated with mortality in AP.', 'To evaluate the usefulness of APACHE II as an early predictor of severity in AP, its correlation with OF, and the relevance of an early establishment of OF during the course of AP.', 'From January 1999 to November 2001, 447 consecutive cases of AP were studied. APACHE II scores and Atlanta criteria were used for defining severity and OF.', 'Twenty-five percent of patients had severe acute pancreatitis (SAP). APACHE II at 24 h after admission showed a sensitivity, specificity, and positive and negative predictive value of 52, 77, 46, and 84%, respectively, for predicting severity. Mortality for SAP was 20.5%. Seventy percent of patients who developed OF did so within the first 24 hours of admission, and their mortality was 52%. Mortality was statistically significant (p< 0.01) if OF was established within the first 24 hours after admission.'] Is early onset of organ failure the best predictor of mortality in acute pancreatitis?