Objective This study was conducted to ascertain whether study on carcinogenic potential of reflux juice from long-standing gastrectomy patients could clarify the relationship between duodenogastric reflux and gastric stump cancer. Methods A total of 48 reflux juice samples(11 Billroth Ⅰ,37 BillrothⅡ)were employed in our study.Ames test and MTT proliferation assay were carried out to evaluate the mutagenicity and proliferative activity of aspirates, respectively. Results There was no difference in mutagenicity of the samples in respect of surgical procedures(P＞0.05). While Billroth Ⅱ samples exhibited stronger proliferative activity than Billroth Ⅰ samples(P=0.751),In addition, the proliferative activity well correlated with pH of aspirates(rs=0.73,P＜0.001),but the mutagenicity failed to this correlation. Conclusion We confirm the duodenal reflux theory for the gastric stump cancer with the aspirates from long-standing postgastrectomy patients, and further suggest that proliferative activity of aspirates should be responsible for the high incidence of gastric cancer in the long-standing gastrectomy patients, thus roviding direct evidence for the etiology of the gastric stump cancer. Simultaneously closely endoscopic surveillance or postgastrectomy patients with moderate/severe dysplasia is highly recommended. In addition, to decrease the incidence of stump cancer effectively, it seems reasonable to perform reconstruction procedures(e.g,Roux-en-Y anastomosis)for those with severe duodenal reflux and to focus the chemoprevention of this cancer on proliferative activity of the reflux juice.