Waldenstrom's macroglobulinemia is an uncommon low-grade B-cell lymphoproliferative disorder in which monoclonal immunoglobulin M is produced. Neurological symptoms due to hyperviscosity are frequent manifestations of Waldenstrom's macroglobulinemia. However, central nervous system infiltration by plasmacytoid lymphocytes (Bing-Neel syndrome) has only rarely been reported. We report a case of a 51-yr-old woman suffering from Waldenstrom's macroglobulinemia who complained of persistant headache. Brain magnetic resonance imaging revealed an extra-axial soft tissue mass along the left cavernous sinus, left tentorium, right tentorium, and falx cerebri. A stereotactic biopsy of dural tissue from the falx was performed and showed plasmacytoid lymphocyte infiltration. The patient became symptom- free with irradiation of the whole brain followed by chemotherapy with fludarabine.