BACKGROUND The hemoglobin threshold for transfusion of red blood cells in patients with acute gastrointestinal (GI) bleeding is controversial. We compared the efficacy and safety of a restrictive transfusion strategy with those of a liberal transfusion strategy. METHODS OBJECTIVE The objective was to prove that the restrictive threshold for red blood cell transfusion in patients with acute upper GI bleeding (UGIB) was safer and more effective than a liberal transfusion strategy. RESULTS In total, 225 patients assigned to the restrictive strategy (51%) and 65 assigned to the liberal strategy (15%) did not receive transfusions (P <0.001). The probability of survival at 6 weeks was higher in the restrictive-strategy group than in the liberal-strategy group (95% versus 91%; hazard ratio (HR) for death with restrictive strategy, 0.55; 95% confidence interval (CI) 0.33 to 0.92; P = 0.02). Further bleeding occurred in 10% of the patients in the restrictive-strategy group and in 16% of the patients in the liberal-strategy group (P = 0.01), and adverse events occurred in 40% and 48%, respectively (P = 0.02). The probability of survival was slightly higher with the restrictive strategy than with the liberal strategy in the subgroup of patients who had bleeding associated with a peptic ulcer (HR 0.70, 95% CI 0.26 to 1.25) and was significantly higher in the subgroup of patients with cirrhosis and Child-Pugh class A or B disease (HR 0.30, 95% CI 0.11 to 0.85) but not in those with cirrhosis and Child-Pugh class C disease (HR 1.04, 95% CI 0.45 to 2.37). Within the first 5 days, the portal-pressure gradient increased significantly in patients assigned to the liberal strategy (P = 0.03) but not in those assigned to the restrictive strategy. CONCLUSIONS Compared with a liberal transfusion strategy, a restrictive strategy significantly improved outcomes in patients with acute UGIB.