BACKGROUND: We investigated the effectiveness of scoring systems, acute inflammation and acute phase responses in the early diagnosis of the severity of acute pancreatitis. METHODS: In a prospective design, we determined Ranson and APACHE II scores, and serum interleukin-6 (IL-6) and C-reactive protein (CRP) levels in 30 patients (21 females, 9 males; mean age 56 years; range 28 to 82 years) with acute pancreatitis. The patients were divided into two groups as mild and severe pancreatitis according to the clinical, biochemical, and computed tomography findings. Ranson and APACHE II scores were determined after 48 hours, IL-6 levels within 24 hours, and CRP levels after 24, 48, and 72 hours of admission. Ranson scores of 4 or above, APACHE II scores of 8 or above, baseline serum IL-6 and CRP levels of 50 pg/ml and 150 mg/L, respectively, were regarded as strong predictors of acute pancreatitis. RESULTS: Severe pancreatitis was diagnosed in six patients (20%), one of whom died due to multiple organ failure. Biliary symptoms were the most common presenting signs in both groups. The mean Ranson (p=0.004) and APACHE II (p=0.001) scores, serum IL-6 (p=0.001) and CRP levels at 24, 48, and 72 hours (p=0.02) were significantly high in patients with severe pancreatitis. The sensitivity was found as 66.6%, 83.3%, 100%, and 83.3%; the specificity as 87.5%, 91.7%, 87.5% and 71%; and the accuracy as 83.3%, 90%, 90%, and 73.3% for Ranson and APACHE II scores, IL-6 and CRP levels, respectively. CONCLUSION: Ranson and APACHE II scores, CRP and, in particular, serum IL-6 levels are strong predictors of severe ancreatitis.