BACKGROUND: Discrepancies exist in reported mortality rates of nonvariceal upper gastrointestinal bleeding (NVUGIB).OBJECTIVE: To perform a systematic review assessing possible reasons for these disparate findings and to more reliably compare them.METHODS: The MEDLINE, EMBASE and ISI Web of Knowledge databases were searched for studies reporting mortality rates in NVUGIB involving adults and published in English. To ensure robust and contemporary estimates, studies spanning 1996 to January 2011 that included more than 1000 patients were selected.RESULTS: Eighteen of 3077 studies were selected. Ten studies used administrative databases and the remaining eight used registries. The mortality rates reported in these studies ranged from 1.1% in Japan to 11% in Denmark. There were variations in reported mortality rates among countries and also within countries. Reasons for these disparities included a spectrum of quality in reporting as well as heterogeneous definitions of case ascertainment, differing patient populations with regard to severity of presentation and associated comorbidities, varying durations of follow-up and different health care system-related practices.CONCLUSIONS: Wide differences in reported NVUGIB mortality rates are attributable to differences in adopted methodologies and populations studied. More uniform standards in reporting are needed; only then can true observed variations enable a better understanding of causes of death and pave the way to improved patient outcomes.