['Our goals were to measure the accuracy of specialist helical computed tomography (CT) in the preoperative staging of gastric cancer, to determine the relative benefit of progressive CT system technology, and to determine the magnitude of any learning curve in radiological interpretation.', 'One hundred patients (median age, 70 years; range 27-86 years; 68 male) underwent a preoperative CT (73 helical [hCT], 27 multislice [mCT]), performed by a single specialist radiologist, followed by surgery within 3 weeks. The strength of the agreement between the perceived CT stage and the histopathological stage was determined for each CT system and also for four serial cohorts of 25 patients, by the weighted Kappa statistic (Kw).', 'The Kw values for T, N, M1 liver, and M1 peritoneal stage were 0.40, 0.18, 0.36, and 0.09 for hCT, compared with 0.57, 0.67, 0.66 (all P < 0.001), and 0.24 (P = 0.06) for mCT. Serial Kw for T and N stages improved from 0.26 and -0.14 in the first quartile of patients to 0.61 and 0.73 (P < 0.001) in the last quartile of patients.'] Do progressive CT system technology and experience improve the perceived preoperative stage of gastric cancer?