Upper GI series and CT scans of 23 patients with advanced gastric cancer were reviewed and correlated to determine CT's capability in detecting gastric tumors. The CT images of the gastric carcinomas revealed either a mass or thickening of the wall. These abnormalities were present in 78% of the cases whereas CT demonstrated a "mass" in 52%. The most difficult site for CT diagnosis of gastric cancer was the antrum. Diagnostic accuracy of CT in evaluating tumor invasion of adjacent structures is reportedly high. However, in the present study this was not necessarily true. In 4 of 5 patients whose gastric tumors proved unresectable, CT failed to reveal adjacent invasion. This suggests that CT is not always reliable in predicting surgical resectability.