OBJECTIVE: The purpose of this study was to identify predictors of malignancy on CT for the evaluation of gastrointestinal stromal tumors of the stomach. MATERIALS AND METHODS: The medical records at our institution of 81 patients with a histologic diagnosis of gastrointestinal stromal tumor of the stomach were reviewed. Two radiologists retrospectively reviewed the CT findings by consensus with respect to lesion size, contour, tumor growth pattern, enhancing pattern, degree of enhancement, mesenteric fat infiltration, ulceration, calcification, lymphadenopathy, direct invasion to adjacent organ, and distant metastasis. Categoric variables were compared using the chi-square or Fisher's exact test. Multiple stepwise logistic regression analysis by means of forward selection was performed to determine significant predictors of high mitotic rate. Univariate analysis and multivariate analysis were also performed in a subgroup of 36 tumors with maximal diameter of 5 cm or smaller. RESULTS: Size, presence of an ulcer, mesenteric fat infiltration, direct organ invasion, and metastasis were more frequently observed during univariate analysis in tumors with a high mitotic rate (p < 0.05). With stepwise logistic regression analysis, the size (odds ratio, 2.57; 95% CI; 1.42-4.67) was the only significant predictor of a high mitotic rate. In a subgroup of 36 tumors 5 cm or smaller, differentiation of benign from malignant tumors was not possible using CT. CONCLUSION: Although presence of an ulcer, mesenteric fat infiltration, direct organ invasion, and metastasis were more frequently observed in tumors with a high mitotic rate, no CT feature, other than size, was found to have predictive value with respect to malignant gastrointestinal stromal tumors of the stomach.