Objective:To test the hypothesis that elevated interleukin (IL)-10 plasma concentration relative to IL-6 and IL-8 in patients with acute pancreatitis is associated with improved clinical outcome.Design:Case series.Setting:University hospital surgical and intensive care unit.Patients:Patients with mild (n = 18) and severe (n = 14) acute pancreatitis were recruited within 12 hrs of admission and studied for 5 days.Interventions:None.Measurements and Main Results:The plasma concentration of IL-10 was significantly elevated in patients with severe pancreatitis during the 5 days and especially so in those who died compared with survivors on day 5 (p<.03). The ratio of IL-10/IL-6 was decreased in patients with severe pancreatitis on day 5 (p< .01). There was a significant decrease in the ratio of IL-10/IL-8, but not of IL-10/IL-6, during the first 5 days (p< .014).Conclusions:The findings are consistent with the hypothesis that an increase in plasma IL-10 relative to IL-6 or IL-8 is associated with improved clinical outcome.