Extramedullary hematopoiesis presented as posterior mediastinal masses in two brothers with thalassemia intermedia. In one patient, acute spinal cord compression developed secondary to epidural hematopoiesis. Laminectomy resulted in complete return of function. The characteristic x-ray picture of the hematopoietic tumors is that of soft, multilobular, paravertebral masses between the sixth and twelfth thoracic vertebrae without evidence of bony erosion. The preferable diagnostic procedure is needle biopsy under direct vision because of the vascularity of the tumor and associated ease of hemorrhage. While surgical therapy is necessary for relief of acute problems such as cord compression, radiation therapy may be effective in relieving minor symptoms.