Myelolipoma is a benign nonepithelial neoplasm composed of mature marrow elements and fat cells. This rare neoplasm is usually discovered by pathologists incidentally at autopsy, and, with rare exceptions, usually occurs in the adrenal glands. One of these exceptional anatomic sites is the mediastinum, and only three cases of primary mediastinal myelolipomas have been documented in the English-language literature (1-3). We are presenting a primary myelolipoma involving the posterior mediastinum that was discovered on routine chest radiographs and successfully resected. Computed tomography (CT) scan findings of this rare mediastinal tumor are also presented. This is the first case report in the English language of primary myelolipoma in the mediastinum that was detected clinically and resected successfully.