A 33-year old man with acquired immunodeficiency syndrome was admitted to Severance hospital following 1 year of diarrhea and 2 to 3 months of low sternal pain. The patient had progressive generalized lymphadenopathy for the previous 3 years. Whole body bone scan for evaluation of bone pain showed multiple abnormal hot uptakes at the low sternal body and T8 and T10 vertebra. Chest CT showed multifocal cortical erosion of the bone with soft tissue mass at the low sternal body and spine MRI showed multiple low-signal density in T1WI and high-signal density in T2WI at the T8 and T10 vertebral body. Biopsy was performed at the sternochondral junction and it showed high-grade malignant lymphoma of the large cell immunoblastic type. Immunostaining showed positive for the B-cell markers (CD79a and L26) and negative for the T-cell marker (UCHL1). Radiotherapy of 3,000 cGy was delivered to the sternum and vertebra. Since then, systemic chemotherapy with m-BACOD regimen (except dexamethasone) and anti-retroviral therapy with a combination of 3 drugs (didanosine, lamivudine, indinavir) has been performed. This is the first case report of primary bone lymphoma associated with acquired immunodeficiency syndrome in Korea.