Bone marrow involvement is infrequent at presentation in cases of diffuse large B-cell lymphoma. We report four adult patients with diffuse large B-cell lymphoma in whom bone marrow involvement with hematologic manifestations was the predominant clinical feature at presentation. Three patients presented with a leukoerythroblastic blood picture and one with pancytopenia. In each case, the unusual hematologic manifestations, with bone marrow replacement and the presence of immature forms in the peripheral blood, led to consideration of alternative hematologic diagnoses, including acute granulocytic leukemia in three cases and a myelodysplastic syndrome in one. The correct diagnoses were established by immunohistochemistry on formalin-fixed, paraffin-embedded bone marrow for two cases and by flow cytometry on aspirated bone marrow or peripheral blood lymphocytes for the other two. Diffuse large B-cell lymphoma should be considered in the differential diagnosis of unusual hematologic presentations, particularly in the elderly.