AIM: To investigate the early upper gastrointestinal endoscopy(endoscopy) significantly reduces mortality resulting from upper gastrointestinal(GI) bleeding. METHODS: Upper GI bleeding was defined as 1a, 1b, 2a, and 2b according to the Forrest classification. The hemoglobin(Hb), and C-reactive protein(CRP) were examined at around the day of endoscopy and 3 mo prior to endoscopy. The rate of change was calculated as follows:(the result of blood examination on the day of endoscopy- the results of blood examination 3 mo prior to endoscopy)/(results of blood examination 3 mo prior to endoscopy). Receiver operating characteristic curves were created to determine threshold values. RESULTS: Seventy-nine men and 77 women were enrolled. There were 17 patients with upper GI bleeding: 12 with a gastric ulcer, 3 with a duodenal ulcer, 1 with an acute gastric mucosal lesion, and 1 with gastric cancer. The area under the curve(AUC), threshold, sensitivity, and specificity of Hb around the day of endoscopy were 0.902, 11.7 g/dL, 94.1%, and 77.1%, respectively, while those of CRP were 0.722, 0.5 mg/dL, 70.5%, and 73%, respectively. The AUC, threshold, sensitivity, and specificity of the rate of change of Hb were 0.851,-21.3%, 76.4%, and 82.6%, respectively, while those of CRP were 0.901, 100%, 100%, and 82.5%, respectively. CONCLUSION: Predictors for upper GI bleeding were Hb < 11.7 g/dL, reduction rate in the Hb > 21.3% and an increase in the CRP > 100%, 3 mo before endoscopy.