A patient with the acquired immune deficiency syndrome (AIDS) and the lymphadenopathic variant of Kaposi's sarcoma developed skin, gastrointestinal and pulmonary lesions. A cellular specimen was obtained on bone marrow aspiration, but the bone marrow biopsy revealed dense reticulin fibrosis with slit-like spaces and endothelial-lined channels consistent with Kaposi's sarcoma. At postmortem examination, Kaposi's sarcoma was found in the pleura and lungs, throughout the gastrointestinal tract, in the liver and spleen, and in the thoracic and abdominal lymph nodes. Bone marrow architecture appeared grossly normal, but microscopic examination revealed numerous foci of Kaposi's sarcoma. This is the first reported example of bone marrow involvement with Kaposi's sarcoma in AIDS recognized antemortem.