Computed tomographic (CT) features in 29 patients with gastrointestinal leiomyomas and leiomyosarcomas were analyzed and compared. Features evaluated included size, shape, homogeneity, response to intravenous contrast material, and presence of calcification. The sarcomas were larger (average, 12 cm) than the myomas (average, 4.8 cm), had an irregular shape, and had a nonhomogeneous appearance both before and after contrast enhancement. Gross features depicted on CT are compared with gross pathologic criteria. Analysis of the CT appearance suggested malignancy in two cases in which microscopic examination was interpreted as benign.