It has been suggested that because propranolol decreases portal venous pressure, it may prevent gastrointestinal bleeding associated with portal hypertension. We randomly assigned 74 patients with cirrhosis, who were admitted because of gastrointestinal bleeding, to either oral propranolol given in doses that reduced the heart rate by 25 per cent (38 patients) or to a placebo (36 patients). The proportion of patients free of recurrent gastrointestinal bleeding one year after inclusion in this study was 96 per cent in the propranolol group and 50 per cent in the placebo group (P less than 0.0001). We conclude that continuous administration of propranolol by mouth is effective in preventing recurrent gastrointestinal bleeding in patients with cirrhosis.