Objective To compare the efficacy of Ranitidine and Pantoprazole for the prevention of haemorrhage from stress ulcer among critical care patients.Methods A total of 121 critically ill patients were included in this retrospective study.The choice of pharmacologic stress ulcer prophylaxis were either Ranitidine or Pantoprazole.The primary outcome was the incidence of stress-related significant upper gastrointestinal bleeding,and the secondary outcome was the incidence of hospital acquired pneumonia (HAP).Results A total of 63 patients were given Ranitidine,and 58 patients were given Pantoprazole for stress ulcer bleeding prophylaxis.Nine patients ( 7.44％,9/121 ) developed clinically-important upper gastrointestinal bleeding,including 5 (7.94％,5/63) in the Ranitidine group,and4 (6.90％,4/58) in the Pantoprazole group.The rate of HAP was 3.17％ (2/63) in the Ramitidine group,and 15.52％ (9/58) in the Pantoprazole group.Conclusion Ranitidine was associated with lower rates of HAP as compared with Pantoprazole,with no statistically significant difference in clinically-important gastrointestinal hemorrhage.Because of limited trial data,future well-designed and powerful randomized,clinical trials are warranted.