The objectives of this study were to evaluate the accuracy of endoscopic ultrasonography (EUS) in local and regional staging of early gastric cancer, to analyze the factors influencing the accuracy of EUS, and to reveal the usefulness and problems of EUS in pre-treatment staging of gastric cancer. We examined 105 lesions in 104 patients with histologically confirmed gastric cancer and retrospectively evaluated them with EUS. The diagnostic accuracy, sensitivity, and specificity of EUS were determined by comparing the pre-treatment EUS with the postoperative histopathological findings. The overall diagnostic accuracy of EUS for the depth of cancer invasion was 86%. The overall sensitivity and specificity were 60% and 96%, respectively. The accuracy significantly declined in lesions located in the upper-third of the stomach (70%). Type 0-I lesions tended to be over-staged (12&), and the upper-third lesions tended to be under-staged (23%). The accuracy significantly declined in differentiated adenocarcinoma with massive submucosal invasion (56.5%). EUS is useful for evaluating the depth of gastric cancer invasion which determines the feasibility of endoscopic treatment. However, it is noteworthy that the diagnostic accuracy of the invasion depth diminished for lesions in the upper third of the stomach
