We will enroll those patients that have received major abdominal surgery and admitted to surgical ICU. After obtaining the consent, we will give them prophylactic drugs for 7 days within 24 hours. They are randomly allocated to 2 groups. Group I: pantoprazole 40 mg iv bolus stat and then qd ; Group II: famotidine 20 mg iv bolus stat and then q12h. We will monitor the following data: operation type & time, APACHE II score, CBC, CXR, stool character and OB test, NG aspirate. If clinical evidence of UGI bleeding occurs, endoscopic examination will be performed. We define the end point as overt bleeding, death or transfer out of ICU. We will compare the prevalence of UGI bleeding and ventilator associated pneumonia in these 2 groups