In order to select the most appropriate treatment for gastric cancer in the cardiac area, precise staging by determining the depth of cancer invasion, and esophageal invasion, and lymph node metastases is important. In this paper, diagnosis of these factors using endoscopic ultrasonography (EUS) and its accuracy are discussed. In 121 cases of gastric cancer in the cardiac area, EUS was performed and the findings compared with the pathological diagnosis. The depth of cancer invasion was accurately determined in 60% of mucosal cancer cases, 83% of cancer invading the submucosa, 50% of cancer invading the muscularis propria or the subserosa, 86% of cancer invading the serosa, 45% of cancer invading other organs, and overall accuracy was 77%. In cases of esophageal invasion sensitivity was 98%, specificity 93%, and overall accuracy 94%. In cases of lymph node metastasis specificity was 78%: 86% for N1 and 72% for N2. EUS therefore has an important role in diagnosis and selection of treatment.