This study was performed to determine the effects of glutamine enriched total parenteral nutrition (TPN) on the patients with acute pancreatitis (AP). Forty patients with AP, who had Ranson's score between 2 and 4 received either standard TPN (control group) or TPN with glutamine (treatment group). The patients in the treatment group received TPN containing 0.3 g/kg/days glutamine. At the end of the study, patients were evaluated for nutritional and inflammatory parameters, length of TPN and length of hospital stay. The length of TPN applications were 10.5+/-3.6 days and 11.6+/-2.5 days, and the length of hospital stays were 14.2+/-4.4 and 16.4+/-3.9 days for the treatment and control groups (NS), and the complication rates in the treatment and control groups were 10 and 40%, respectively (P<0.05). The transferrin level increased by 11.7% in the group that received glutamine-enriched TPN (P<0.05), whereas the transferrin level decreased by 12.1% in the control group (NS). At the end of the study, slight but not significant changes were determined in both groups in fasting blood sugar, albumin, blood urea nitrogen (BUN), creatinine, total cholesterol concentrations, aspartate aminotransferase (AST), alanine transaminase (ALT) and lactate dehydrogenase (LDH) activities, leukocytes, CD(4), CD(8), serum Zn, Ca and P levels compare to the baseline levels (NS). Significant decreases were determined in serum lipase, amylase activities and C-reactive protein (CRP) levels in both groups (P<0.05). The results of this study have shown that glutamine supplementation to TPN have beneficial effects on the prevention of complications in patients with AP.