Nonsteroidal antiinflammatory drugs (NSAIDs) are used in the treatment of extensive diseases related to various symptoms; inflammation, pain and fever. NSAIDs work by blocking prostaglandin synthesis, but adverse drug events (ADEs) have been increasing dramatically such as gastrointestinal bleeding, perforation and stenosis, a kind of serious ADEs. Therefore, NSAID-related ulcer complication guidelines have been announced containing various risk factors and symptoms. Thus, this study aims to evaluate of NSAID usage and appropriateness for prevention of NSAID-related ulcer complication based on American journal of gastroenterology (AJG) guideline 2009. Further, the study suggests Korean guideline for prevention of NSAID-related ulcer compared to AJG guideline. For this study, data was collected through electronic medical record (EMR) at Seoul national university of Bundang hospital. The primary end point was a composite of NSAID-related ulcer risk factor, types of NSAIDs, co-prescribed NSAID ulcer prevention drugs and NSAID-related ulcer after taking NSAID. The risk factors include over 65 years, high dose NSAID, previous ulcer history and taking drugs (e.g. aspirin, anticoagulant and steroid) causing ulcer. If a patient has 3 or 4 factors, that patient was classified high risk group. And if 1 or 2 factors that patient was classified moderate risk group. The patient who has no risk factor was in low risk group. I studied 8,120 patients who received NSAID from 1 January 2009 to 31 December 2009. High risk group was 16(0.2%), moderate risk group was 4,364(53.7%), and low risk group was 3,740(46.1%). The results show that high risk group should be prescribed COX-2 inhibitors with ulcer prevention drugs, and moderate or low risk group need traditional NSAIDs with ulcer prevention drugs. This may be different with 2009 AJG guideline because AJG guideline suggested taking COX-2 inhibitor alone in moderate group or taking traditional NSAID alone in low risk group could get higher ulcer complication. The results indicated that choosing preventive drug is important in case that how many risk factors the patients have. The proper drugs would be helpful for safe and effective NSAID usage in each patient group.