AIM:To assess risk factors for bleeding after gastric endoscopic submucosal dissection(ESD) and to develop preventive measures.METHODS:This retrospective study was performed in a tertiary referral center.A total of 328 patients underwent ESD for 398 gastric neoplasms between July 2007 and June 2009.The main outcome was association between post-ESD bleeding and the following:age;sex;comorbidities;daily use of medicine potentially related to gastric injury/bleeding;location,size,and histological depth of lesions;ulceration;experience of operator coagulating the ulcer floor,and duration of operation.We also determined the relationship between the location of post-ESD bleeding and risk factors for hemorrhage.RESULTS:Univariate analysis revealed significant risk factors:tumor location [odds ratio(OR),2.86;95% CI:1.21-6.79,P=0.024],coagulator experience(OR,4.29;95% CI:1.43-12.86,P=0.009),and medicine potentially related to gastric injury/bleeding(OR,2.80;95% CI:1.14-6.90,P=0.039).Multivariate logistic regression analysis confirmed significant,independent risk factors:tumor in lower third of stomach(OR,2.47;95% CI:1.02-5.96,P=0.044),beginner coagulator(OR,3.93;95% CI:1.29-11.9,P=0.016),and medicine(OR,2.76;95% CI:1.09-6.98,P=0.032).We classif ied cases of post-ESD bleeding into two groups(bleeding at the ulcer margin vs bleeding at the center) and found that bleeding at the margin occurred more frequently with beginner coagulators compared with experts(OR,16.00;95% CI:1.22-210.59,P=0.040).CONCLUSION:Beginner coagulators,tumor in the antrum,and medicines were significant risk factors for post-ESD bleeding.Bleeding at the ulcer margin frequently occurred with beginner operators. AIM: To assess risk factors for bleeding after gastric endoscopic submucosal dissection (ESD) and to develop preventive measures. METHODS: This retrospective study performed in a tertiary referral center. A total of 328 patients underwent ESD for 398 gastric neoplasms between July 2007 and June 2009. The main outcome was association between post-ESD bleeding and the following: age; sex; comorbidities; daily use of medicine potentially related to gastric injury / bleeding; location, size, and histological depth of lesions; ulceration; experience of operator coagulation the ulcer floor, and duration of operation. We also determined the relationship between the location of post-ESD bleeding and risk factors for hemorrhage. We also determined the relationship between the location of post-ESD bleeding and risk factors for hemorrhage. % CI: 1.21-6.79, P = 0.024], coagulator experience (OR, 4.29; 95% CI: 1.43-12.86, P = 0.009) and drug potentially related to gastric injury / 1.14-6.90, P = 0.039) .Multivariat e logistic regression analysis confirmed significant, independent risk factors: tumor in lower third of stomach (OR, 2.47; 95% CI: 1.02-5.96, P = 0.044) P = 0.016), and medicine (OR, 2.76; 95% CI: 1.09-6.98, P = 0.032) .We classified cases of post-ESD bleeding into two groups (bleeding at the ulcer margin vs bleeding at the center) and found that bleeding at the margin occurred more frequently with beginner coagulators compared with experts (OR, 16.00; 95% CI: 1.22-210.59, P = 0.040) .CONCLUSION: Beginner coagulators, tumor in the antrum, and medicines were significant risk factors for post-ESD bleeding.Bleeding at the ulcer marginat occurred with beginner operators.