A 71-year-old woman with multiple myeloma (MM) in remission was admitted for evaluation of recent abdominal distension and was diagnosed as having massive myeloma ascites. The fluid was characterized by a total nucleated cell count of 6,600/mm 3 (67% plasma cells), with a plasma cell CD38+ phenotype. Chemical analysis of the fluid showed lactate dehydrogenase of 122 IU/L, total protein of 2.9 g/dL, albumin of 2.4 g/dL, diastase of 38 IU/dL, cholesterol of 46 mg/dL, and C-reactive protein of 3 g/dL. The serum-ascites albumin gradient (SAAG) was low (0.9). Electrophoresis of the ascitic fluid showed a monoclonal spike in the gamma region and immunoelectrophoresis confirmed the presence of lambda light chains similar to those seen in the urine. Further analysis of the ascitic fluid showed markedly elevated levels of โค 2 microglobulin (11,161 ยตg/L) and interleukin-6 (146 pg/ml compared to serum level of 4.3 pg/ml). There was evidence of intraabdominal masses that completely resolved with continuous high-dose cyclophosphamide (750 mg/m 2 /day for four days) followed by clinical improvement and disappearance of the ascites. We stress the value of complete fluid characterization and intensive chemotherapy to achieve a favorable outcome.