To evaluate the value of each MRI findings iu differentiating tbe nature of soft tissue lesions. Subjects and Methods: We performed a blind retrospective review of MR imaging in 65 consecutive soft-tifsue lesions (cystic leaions ln or around the joints, and the soft tissue abnormalities directly related to a known trauma were excluded). Morphology and signal intensity characteristics were analyzed. Each lesion was considered as benign tumor malignant tumor, benign but locally aggressive lesion, and undetermined. The final diagnosis was established pathologically (n = 45), and by the association of other imaging studies, clinical ihlings and follow-up over 2 yr (n = 20). Results: Involvement of one compartment was equal in malignant (57.1%) and benign (56.2%) tumors, whereas multicompartmental involvement was most common in non-tumoral lesions (39.1%) (P<O.O5). Welldefined margins were most frequent in benign tumors (189.2%) (P<O.O5). Tbe change from homogeneous to heterogeneous pattern on Tl-and T2-weighted sequences as a predictor of malignancy showed a sensitivity of 77.7% and a specificity of 20%. Based on the MRI fimlings a diagnosis of benign lesion was eshblisbed with a sensitivity of 60.7% and a specificity of 77.7%; malignant tumor with a sensitivity of 78.5% and a specifkity of 96% and benign locally aggressive lesions with 54.5% and 88.1%, respectively. With the addition of the clinical data, an etiologic diagnosis was performed in 78.5% benign tumors, in 85.7% malignant tumors, and in 95.6% benign non&moral lesions. Undetermined lesion was diagnosed iu eight masses. Conclusion: SoA tissue lesions can be diagoosed with certainty in many benign tumors based on the integrated evaluation of morphology and signal intensity MR hdings. Tbe association of MR and clinical data allowed us to ident@ benign but locally aggressive lesions, mostly related to iofection. MR findings are bigbly speciik for malignant tumor, although a histologic diagnosis cannot be performed based only on image analysis. When a mass is undetermined and no criteria for benignity or malignancy can be established, pathologic analysis should be. always performed.