Background and Study Aims: Endosonography (EUS) has been shown to be more accurate than incremental computed tomography (CT) in the local (T) and regional (N) staging of gastric carcinoma; however, EUS has never been compared with helical CT (HCT). The fifth edition of the TNM classification changed the guidelines for N-staging of gastric carcinoma. The accuracy of imaging methods in this new system remains unknown. Patients and Methods: Staging accuracy of EUS and HCT were compared prospectively with pathological or intraoperative findings in 88 gastric carcinoma patients. Staging was done according to the fourth and fifth editions of the TNM classification. EUS was done with a radial echo endoscope, and HCT with a scanner with two rows of detectors (two-phase contrast-enhanced scanning of a water-filled stomach). Results: The T-staging accuracy of EUS (63 %, CI 52 - 73 %) was superior to the accuracy of HCT (44 %, CI 34 - 55 %; P = 0.021). N-staging accuracy of both methods was similar when the fourth edition of the TNM classification was used (EUS 47 %, CI 34 - 60 %; HCT 52 %, CI 38 - 65 %). However, HCT was more accurate than EUS when the fifth edition of the classification was applied (EUS 30 %, CI 18 - 43 %, HCT 47 %, CI 34 - 60 %; P = 0.044). The accuracy of detection of lymph node metastases was similar for both methods (EUS 67 %, CI 54 - 78 %; HCT 77 %, CI 64 - 86 %). Conclusions: EUS is more accurate than HCT in the T-staging of gastric carcinoma. Both methods are comparable for N-staging, when this is done according to the older, fourth edition of the TNM classification. If the fifth edition is used, EUS is less accurate than HCT.