&NA;Bone marrow involvement by large B‐cell lymphoma usually occurs in patients with widely disseminated disease. Rare cases may appear initially in the bone marrow, usually with evidence of concurrent hepatic and/or splenic involvement. The author presents a case of “marrow‐only” large B‐cell lymphoma and reviews the previous literature, contrasting it with the more common bone and bone marrow manifestations of large cell lymphoma. The author also considers the primary differential diagnoses including small noncleaved cell lymphoma/L3 acute lymphoid leukemia, anaplastic myeloma, and acute myelogenous leukemia. Correlation with the clinical features, peripheral blood findings, and morphologic features of the biopsy and aspirate allows distinction between these entities. Immunostaining and/or flow cytometric immunophenotypic analysis can provide confirmation of the diagnosis.