Purpose: Preoperative staging of gastric cancer is crucial because the treatment modality and the prognosis depend upon the stage of gastric cancer. Current treatment modalities for early gastric cancer have focused on the quality of life. Endoscopic ultrasonography (EUS) and abdominal computed tomography (CT) are commonly used diagnostic tools to evaluate the invasiveness (T stage) of the primary tumor. The purpose of this paper is to evaluate the sensitivity and the specificity of preoperative EUS and CT in comparison with postoperative pathology. Materials and Methods: From October 2001 to October 2002, EUS and abdominal CT were performed simultaneously on 75 patients who underwent radical gastric surgery for the treatment of gastric cancer. Through analyzing the clinical T stage and the pathologic T stage, We evaluated the diagnostic sensitivities and specificities of endoscopic ultrasonography and abdominal computed tomography. Results: The male-to-female sex ratio was 1 : 0.6 (males: 47, females: 28). The mean age was 55.4 years in males (range: $28~81$) and 54.4 years in females (range: $23∼77$). The clinical T stage based on EUS included 22 T1mm, 7 T1sm, 22 T2, and 24 T3. The clinical T stage based on CT included 20 Tx, 23 T2, and 32 T3. The permanent pathologic report confirmed 23 T1mm, 10 T1sm, 17 T2, 24 T3, and 1 T4. The sensitivity and specificity of EUS were $84.2\%;and;94.7\%$, respectively. However, the sensitivity and specificity of abdominal CT were $53.3\%;and;77.0\%$, respectively. Conclusion: Our data suggest that EUS is a very useful diagnostic tool for evaluating the T stage of gastric cancer because EUS has higher specificity than abdominal CT. Therefore, EUS may have a significant role as a preoperative diagnostic modality in patients undergoing minimally invasive surgery.