Primary non-Hodgkin's lymphoma (NHL) of the breast is a rare entity that does not have a well-defined treatment strategy. At presentation, most patients are clinically thought to have a primary breast carcinoma, and the diagnosis of lymphoma is made at biopsy. Once the diagnosis of lymphoma is made, patients are treated with some combination of chemotherapy, radiation therapy, and surgery. We review The Cleveland Clinic Foundation experience with primary breast lymphoma. Between 1980 and 1996, 17 patients with primary breast lymphoma were seen at The Cleveland Clinic Foundation, and 13 had follow-up information available. All patients underwent a staging workup including computed tomography (CT) scan of the chest, abdomen, and pelvis, as well as bilateral bone marrow biopsies; all patients staged IE (breast involvement only) or IIE (limited to the breast and ipsilateral axilla) were included. We did not include patients with more extensive supradiaphragmatic nodal involvement who were stage IIE. Patients received some combination of surgery, radiation, and chemotherapy. The median follow-up was 34 months, with a range of 7 to 138 months. There was an equal incidence of right- versus left-sided lesions. Five patients survived at least 5 years from the time of diagnosis. Long-term survival in patients with primary NHL of the breast is possible. We recommend treating patients with aggressive NHL of the breast with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) chemotherapy, followed by involved field radiation and treating those patients with indolent lymphoma with involved field radiation alone.