18 malignant lymphomas with initial manifestation in bone were selected from the Bone Tumor Registry of Westfalia at the Münster Institute of Pathology where they had been documented between 1975 and 1985, and evaluated under clinical, radiological and histological aspects. Non-Hodgkin lymphomas were reclassified according to the Kiel nomenclature. Paraffin-embedded material was subjected to immunohistochemical analysis in order to assess the features that could add to the correct characterization of these lymphomas, and to their differentiation from other round cell tumors of bone. Non-Hodgkin lymphomas (NHL) were more common in the collective than Hodgkin's lymphomas (HL). Of 13 NHL, 2 were of low, 11 of high-grade malignancy. The former comprised one centrocytic and one centroblastic/centrocytic, the latter 7 centroblastic, 2 immunoblastic, and 2 lymphoblastic lymphomas. Seven NHL patients with localized tumors survived up to 11 years (mean survival span: 6 yrs) after local therapy (radiation and/or resection). Another NHL patient, however, had multiple bone lesions, and died within a year. Analysis for leukocyte common antigen was positive in 9/12 NHL cases, reaction with Ki-B-3, a marker of B-lymphocytes, was positive in 7/12 cases. No lymphoma cells were found to react positively with lysozyme, alpha 1-antitrypsin, or alpha 1-antichymotrypsin. It is concluded that localized lymphomas of bone respond well to appropriate local therapy; immunohistochemical investigation may be useful to characterize the true cellular origin of these tumors, and may help to differentiate them from other round cell tumors of bone.