AIM:Current study was aimed to evaluate the usefulnessof EUS in TNM staging of gastric cancer by comparing EUSpreoperative staging with pathological findings,and thepreliminary exploration of possible reasons for overstagingand understaging phenomenon was especially intended.METHODS:A total of 35 patients with histologicallyconfirmed gastric adenocarcinoma were referred to EUS andstaged preoperatively by using the TNM system.Thepreoperative endosonographic results were compared withthe histopathological staging.RESULTS:The overall accuracy of EUS for determinationof the T stage was 80.0 %,and for T1,T2,T3,and T4 was100 %,71.4 %,87.5 % and 72.7 %,respectively.For Nstage,EUS had the accuracy of 68.6 %,with sensitivity andspecificity of 66.7 % and 73.7 %,respectively.Resectabilitywas predicted with sensitivity and specificity of 87.5 % and100 %,respectively.CONCLUSION:EUS is an accurate staging modality in mostcases,with a few exceptions of overstaging and understaging.Patients with gastric cancers can benefit from preoperativeEUS staging for establishing individualized therapy.However,EUS criteria to differentiate benign from malignant nodesstill need to be further defined by future studies. AIM: Current study was aimed to evaluate the usefulness of EUS in TNM staging of gastric cancer by comparing EUS preoperative staging with pathological findings, and the preliminary study of possible reasons for overstaging and understaging phenomena was particularly intended. METHODS: A total of 35 patients with histologically confirmed gastric adenocarcinoma were referred to EUS and staged preoperatively by using the TNM system. The operative endosonographic results were compared with the histopathological staging. RESULTS: The overall accuracy of EUS for determination of the T stage was 80.0%, and for T1, T2, T3, and T4 was 100% 71.4%, 87.5% and 72.7% respectively. For Nstage, EUS had the accuracy of 68.6%, with sensitivity and specificity of 66.7% and 73.7%, respectively. Rectability was predicted with sensitivity and specificity of 87.5% and 100%, respectively. CONCLUSION: EUS is an accurate staging modality in mostcases, with a few exceptions of overstaging and understaging. Patients with gastr ic cancers can benefit from preoperativeEUS staging for establishing individualized therapy.However, EUS criteria to differentiate benign from malignant nodesstill need to be further defined by future studies.