The aim of this study was to compare the sensitivity, specificity, and diagnostic accuracy of serum interleukin-6, interleukin-8, beta 2-microglobulin, and C-reactive protein in the assessment of the severity of acute pancreatitis using commercial kits for their respective assays. Thirty-eight patients with acute pancreatitis (25 men, 13 women, mean age 59 years, range 16-97) were studied; the diagnosis was based on prolonged upper abdominal pain associated with a twofold increase of serum lipase, and it was confirmed by imaging techniques. According to the Atlanta criteria, 15 patients had severe illness and 23 had mild disease. The four serum markers were determined in all patients on admission, as well as daily for the following five days. On the first day of the disease, the sensitivity (calculated on patients with severe pancreatitis), specificity (calculated on patients with mild pancreatitis), and the diagnostic accuracy of these serum markers for establishing the severity of acute pancreatitis were 100%, 86%, and 91% for interleukin-6 (cutoff level 2.7 pg/ml); 100%, 81% and 88% for interleukin-8 (cutoff level 30 pg/ml); 58%, 81%, and 73% for beta 2-microglobulin (cutoff level 2.1 mg/liter); and 8%, 95%, and 64% for C-reactive protein (cutoff level 11 mg/dl). The results of our study indicate that, when assayed during the first 24 hr of disease onset, interleukin-6 and interleukin-8 are better markers than beta 2-microglobulin or C-reactive protein for evaluating the severity of acute pancreatitis.