Background/aims: Because of their vasoactive effects, somatostatin and its analogs are increasingly used in the management of complications of portal hypertension, such as variceal bleeding. Intravenous somatostatin decreases acid secretion, splanchnic blood flow and portal pressure, but the evidence for its efficacy in the treatment of non-variceal upper gastrointestinal bleeding is controversial. The aim of this study was to evaluate the vasoactive effect and possible role of somatostatin infusion in the cessation of non-variceal upper gastrointestinal bleeding. Methods: Fifteen patients with nonvariceal upper gastrointestinal bleeding and without portal hypertension were included. Somatostatin infusion was administered at a dose of 250 mgr/hour for 72 hours. Superior mesenteric arterial average flow velocity, SMA pulsatility index (SMA-PI), portal venous volume flow and renal artery resistance index (RA-RI) were measured two times for each patient by doppler ultrasound; one on the first day of infusion therapy and the second over six hours after stopping the infusion. Wilcoxon signed rank test was used for statistical analyses. Results: The 15 patients (seven male, eight female, mean age: 43.7±8.5 years) given somatostatin infusion had a portal venous volume flow of 32.5±13.2 cm3/sec during infusion while after discontinuation it increased to 53.2±14.6 cm3/sec (p=0.002). Superior mesenteric arterial average flow velocity was found to be 40.1±12.2 cm/sec and 62.7±17.8 cm/sec during somatostatin infusion and after cessation of somatostatin respectively (p=0.014). SMA-PI was also found to be lower during somatostatin infusion at 2.1±0.7 versus 2.9±0.7 without somatostatin infusion (p=0.035). However; RA-RI showed no change with somatostatin infusion (p=0.128). Conclusion: Somatostatin infusion causes a decrease in arterial blood flow to the stomach and duodenum in patients with non-variceal upper gastrointestinal bleeding without portal hypertension. Somatostatin therapy also decreases portal blood flow but renal blood flow is not altered.