In summary, MR imaging is the preferred modality for the evaluation of a soft tissue mass after plain films have been taken. The radiologic appearance of certain soft tissue tumors or tumorlike processes such as myositis ossificans, benign fatty tumors, intramuscular hemangiomas, pigmented villonodular synovitis, and certain hematomas may be sufficiently unique to allow a strong presumptive radiologic diagnosis. It must be emphasized that MR cannot reliably distinguish between benign and malignant lesions, and when radiologic evaluation is nonspecific, one is ill advised to suggest a lesion is benign or malignant solely on the basis of its MR appearance. CT may be useful in specific instances for the identification of subtle soft tissue mineralization in those patients in whom lesions are not adequately evaluated by radiographs. Ultrasonography may be useful in the assessing of recurrent disease as well as in establishing tumor vascularity.