A 31-year-old man with beta-thalassemia intermedia who had undergone splenectomy presented with subjective fever. The physical examination was normal. Chest radiography revealed a well-circumscribed shadow behind the heart (Panel A, arrows). A nonenhanced computed-tomographic scan of the thorax showed two paraspinal soft-tissue masses without any adjacent bone erosion, extending from T7 through T10 (Panel B, arrows). Since there was no previous image for comparison, a biopsy was performed to make a definitive diagnosis among several possible conditions, which included neural and mesenchymal tumors, metastases, hematomas, and extramedullary hematopoiesis. Results on histopathological examination of the biopsy specimen were consistent with extramedullary hematopoiesis (Panel C). No fever was detected during the course of the patient's hospitalization. Foci of extramedullary hematopoiesis may develop in patients with thalassemia owing to erythroid hyperplasia, which may appear as masses in the thoracic or pelvic cavities or sinuses and can mimic the clinical picture of a tumor. The patient reported having no other symptoms during 6 months of clinical follow-up.