Background: Bacterial infections are more frequent in cirrhotic patient who admitted with acute gas-trointestinal hemorrhage compared with others.  The incidences of infection reported in the world literatures were ranged from 14-67% with an overall incidence of 44%.  The incidence of bacterial infection in cirrhotic patients inKing Chulalongkorn Memorial Hospital was 30 % in 2001, usually occurred during the first three days of hospitalization.Objective: To compare the effectiveness of a three-days course norfloxacin with a seven-days course to prevent bacterial infection during admission in cirrhotic patients with acute upper gastrointestinal hemorrhage. Patients and Methods: From October 2002 until December 2003, all cirrhotic patients presented with acute upper gastrointestinal hemorrhage underwent gastroscopy within 24 hours and treated according to the endoscopic findings.  During the first 24 hours of admission, blood, urine and ascitic fluid were sent for culture.  After that, the patients were randomly allocated into two groups: group 1 received norfloxacin 400 mg twice a day for 3 days, group 2 received norfloxacin 400 mg twice a day for 7 days.  All of them were observed for signs of bacterial infection during hospitalization and treated appropriately.Results: Six patients (20.7%) from group 1 and none of the patients from group 2 developed infections. UTI and bacteremia were proved in two cases.  All of the organisms isolated were gram-negative rods.  The time of appearance of the infection was in the first three days of hospitalization.  There was no mortality in both groups.Conclusions: Three-days course norfloxacin 400 mg twice a day may be sufficient for prevention of bacterial infection in cirrhotic patients with acute upper gastrointestinal hemorrhage.