OBJECTIVE A single institution's experience with the treatment of localized primary malignant lymphoma of bone (PLB) was analyzed to identify major prognostic factors, toxicity, and optimal treatment for this rare malignancy. METHODS A retrospective analysis of 45 previously untreated patients with Ann Arbor stage IE and IIE PLB from 1967 to 1992 was undertaken. All histopathologic material was reviewed. Irradiated patients received at least 40 Gy. Systemic chemotherapy was generally doxorubicin based. Overall survival (OS), progression free survival (PFS), and disease-specific survival (DSS) were calculated actuarially. RESULTS Histologically, there were 41 diffuse large cell, 2 diffuse mixed cell, 1 lymphocytic, and 1 lymphoblastic lymphomas. International Index scores were assessed on 43 patients. Thirty-six patients were treated with chemotherapy and radiation (CMT), five patients were treated with radiation only, and four patients were treated with chemotherapy only. Univariate analysis revealed significantly improved 5-year OS for those patients who had International Index scores of 0 vs. scores of 1 or 2 (85 vs. 53%, respectively, p = 0.004). Analysis failed to demonstrate a difference in OS, PFS, or DSS when comparing radiotherapy alone versus CMT, stage IE vs. stage IIE, or axial skeleton involvement vs. extremities. CONCLUSIONS The outcome of patients with PLB is relatively favorable in the era of CMT. Doses of radiation in the range of 46 Gy provide optimal local control with an acceptable rate of complications. The International Index is a valid prognostic tool for PLB.