The authors made comparative studies of CT findings with upper GI series and surgical finding in 20 cases of histologically proven gastric cancers. The identification of thickening of gastric wall and local and remote metastasis by CT was thought to be great value in treatment planning and prediction of prognosis of the patients. The results were as follows : 1. Of 20 cases, 19 cases demonstrated thickening of gastric wall. Among 3 cases suggested as early cancer on upper GI series, 2 cases demonstrated thickening gastric wall on CT and it was proved to be advanced cancer at surgery. 2. Out of 8 cases showed no definite metastasis on CT, 4 cases had malignant infiltration histoligically in th regional lymph node. But they were less than 1.5cm in diameter. 3. The frequency order or remote metastasis found by CT was pancreas, liver, left adrenal gland and lung in organs and retroperitoneal, retrocrural and regional nodes in lymph nodes.