To assess the efficacy of selective intestinal decontamination with norfloxacin in the prevention of bacterial infections in cirrhotic patients with gastrointestinal hemorrhage, 119 patients were included in a prospective randomized study. Group 1 (n = 60) received norfloxacin orally or through a nasogastric tube, 400 mg twice daily for 7 days beginning immediately after emergency gastroscopy; group 2 (n = 59) was the control group. We found a significantly lower incidence of infections (10% vs. 37.2%; P = 0.001), bacteremia and/or spontaneous bacterial peritonitis (3.3% vs. 16.9%; P less than 0.05), and urinary infections (0% vs. 18.6%; P = 0.001) in patients receiving norfloxacin, as a consequence of decrease in the incidence of infections caused by aerobic gram-negative bacilli. The decrease in mortality observed in the treated group (6.6% vs. 11.8%) did not reach statistical significance. The cost for antibiotic treatment showed a 62% reduction in the treated group compared with the control group. The results show that selective intestinal decontamination with norfloxacin is useful in preventing bacterial infections in cirrhotics with gastrointestinal hemorrhage.