PURPOSE: To assess the diagnostic accuracy of CT scanning in the lymph nodal staging of gastric carcinomawhen a new TNM system is applied, and to compare the accuracy of CT staging between this new system and an earlierone. MATERIALS AND METHODS: Fifty-five patients with biopsy proven gastric carcinoma underwent preoperative CTscanning for staging and surgery. Using both new and earlier TNM systems for each patient, two radiologistsprospectively determined lymph nodal staging, as seen on CT, and reached a consensus. Regional lymph n-odes wereconsidered metastatic when their short transverse diameter was greater than 6-11mm, according to anatomic site. CTlymph nodal staging using the new and the earlier TNM system was compared with surgical and pathologic findings. RESULTS: The overall accuracy of CT scanning in lymph nodal staging was 54.5% with the new TNM system, and 58.1%with the earlier system. There was no statistically significant difference between the two systems (McNemar andchi-square test, p > 0.05). Using the new TNM system, the diagnostic accuracy of CT scanning for N0 was 75%, forN1 58.3%, and for N2 20%; three cases of pathologically proven N3 were not diagnosed. Using the previous system,the accuracy of CT scanning was 75% for N0, 46.7% for N1 and 40% for N2. The diagnostic accuracy of both TNMsystems, especially the new one, significantly decreased as nodal stage in-creased. CONCLUSION: With regard tolymph nodal staging, the diagnostic accuracy of CT scanning did not increase when a new rather than an earlier TNMsystem was used. Diagnostic accuracy significantly decreased in re-verse proportion to nodal stage.