We report on the clinical and imaging features--including CT and MRI--of nodular fasciitis with cortical involvement in the shoulder. Nodular fasciitis is a commonly encountered benign soft-tissue fibrous tumor that typically involves the upper extremity and may be mistaken for a sarcomatous lesion because of its rapid growth. Lesions of the intramuscular subtype, because of their large size and deep location, usually require preoperative MR-imaging. This case is the first reported to our knowledge of nodular fasciitis producing erosion of the cortical surface in the appendicular skeleton.