Primary skeletal lymphoma is an uncommon tumor whose appearance on plain-film radiographs has been well described. However, few reports have described the appearance of this neoplasm on magnetic resonance imaging. As in the primary skeletal lymphoma described, magnetic resonance imaging can be used to define the extent of the tumor and the degree of soft tissue and bone marrow involvement. It can also help to determine the biopsy site and to monitor the tumor's response to radiation therapy.