PURPOSE: The Purpose of this study was to evaluate the usefulness of Helical CT in the preoperative staging of gastric carcinoma. MATERIALS AND METHODS: We performed Helical CT on 66 patients with pathologically proved gastric carcinoma. The findings were prospectively analyzed and correlated with surgical and histopathologic findings. RESULTS: The detection rate for gastric carcinoma was 88%(58/66). The rates of accuracy, understaging, and overstaging of Helical CT according to TNM staging in determining the depth of tumor invasion were 68%(45/66),23%(15/66), and 9%(6/66), respectively. In early and less advanced carcinomas(T1 & T2), the depth of tumor invasion was correctly determined in only 44%(11/25) of cases, whereas in more advanced carcinomas (T3 & T4), the corresponding figure was 83%(34/41). In lymph node staging, accuracy, understaging, and overstaging rates were 62%(41/66), 21%(14/66), and 17%(11/66), respectively. Helical CT showed a sensitivity of 48%, a specificity of97%, and an accuracy of 92% in assessing metastasis to lymph nodes. One of five cases of peritoneal carcinomatosis(20%) was correctly diagnosed by Helical CT. CONCLUSION: In the preoperative evaluation of gastriccarcinoma, Helical CT is useful in the detection of tumours and for determining the depth of tumor invasion, particularly in cases where there is serosal and adjacent organ invasion; for the evaluation of metastasis tolymph nodes and peritoneal carcinomatosis its usefulness is limited, however. Further resech will therefore be necessary.