Purpose: The efficacy of octreotide in the treatment of acute pancreatitis is controversial. Octreotide treatment for acute pancreatitis often shows poor correlation between results obtained in experimental studies and results of clinical trials. In a clinical setting, there is always a delay between the onset of the disease and initiation of the octreotide treatment. The aim of this study is to investigate the relationship between the beginning of treatment and alteration in effectiveness of octreotide. Methods: Acute pancreatitis was induced by pancreatic duct ligation in 50 rats. The rats were randomly divided into five groups. Octreotide was not used in group 1 (control group). Only single dose (4 μg/kg) octreotide was administered subcuta-neously to rats in group 2, having induced pancreatitis. Octreotide treatment was begun at different times (8th, 24th, 48th hour) in three other groups and continued treatment at a dosage of 4 μg/kg t.i.d. The animals were sacrificed at the end of the 72nd hour and blood and tissue samples were collected. Results: Leukocyte count and plasma amylase values were less in groups 2 and 3. Hemorrhagic focuses were encountered less at pancreas tissues in group 3. Pancreatic necrosis and alveolar capillary basal membrane damage were lower in groups 3 and 4. No difference was found in fasting blood glucose, calcium and hematocrit. Conclusion: Octreotide had benefical effects in acute pancreatitis when octreotide treatment was begun in the first 24 hours. Copyright © 2012, the Korean Surgical Society.