PURPOSE: To correlate the preoperative staging of gastric adenocarcinoma using two-phase spiral CT withpathologic staging. MATERIALS AND METHODS: One hundred and eighty patients with gastric cancers confirmed duringsurgery underwent two-phase spiral CT, and were evaluated retrospectively. CT scans were obtained in the proneposition after ingestion of water. Scans were performed 35 and 80 seconds after the start of infusion of 120mL ofnon-ionic contrast material with the speed of 3mL/sec. Five mm collimation, 7mm/sec table feed and 5mmreconstruction interval were used. T- and N-stage were determined using spiral CT images, without knowledge of thepathologic results. Pathologic staging was later compared with CT staging. RESULTS: Pathologic T-stage was T1 in70 cases(38.9%), T2 in 33 (18.3%), T3 in 73 (40.6%), and T4 in 4 (2.2%). Type-I or IIa elevated lesions accountedfor 10 of 70 T1 cases(14.3%) and flat or depressed lesions(type IIb, IIc, or III) for 60 (85.7%). PathologicN-stage was N0 in 85 cases(47.2%), N1 in 42 (23.3%), N2 in 31 (17.2%), and N3 in 22 (12.2%). The detection rate ofearly gastric cancer using two-phase spiral CT was 100.0%(10 of 10 cases) among elevated lesions and 78.3%(47 of60 cases) among flat or depressed lesions. With regard to T-stage, there was good correlation between CT image andpathology in 86 of 180 cases (47.8%). Overstaging occurred in 23.3%(42 of 180 cases) and understaging in 28.9%(52of 180 cases). With regard to N-stage, good correlation between CT image and pathology was noted in 94 of 180cases (52.2%). The rate of understaging(31.7%, 57 of 180 cases) was higher than that of overstaging(16.1%, 29 of180 cases)(p<0.001). CONCLUSION: The detection rate of early gastric cancer using two-phase spiral CT was 81.4%,and there was no significant difference in detectability between elevated and depressed lesions. Two-phase spiralCT for determing the T- and N-stage of gastric cancer was not effective ; it was accurate in abont 50% of casesunderstaging tended to occur.