A 55-year-old man presented with nerve compression and examination of tissue removed by laminectomy, and bone marrow aspiration was diagnostic of multiple myeloma. Protein studies showed a total serum protein of 5.7 g/dL, with a M-component in the fast beta region. The abnormal protein reacted only with anti-lambda antisera but not with antisera from multiple sources in four different laboratories, against known heavy chain and kappa-chain determinants. A marked difference in potency of commercial anti-lambda antisera was noted. The reaction was primarily demonstrable in serum and present only in 100-times concentrated urine. Gel filtration disclosed a molecular weight of 84,000. The patient has been followed for the past four years and has not demonstrated significant proteinuria. The English and Japanese literature records seven cases of tetrameric Bence Jones multiple myeloma or plasma cell dyscrasia. This case appears to be the eighth recorded cases of tetrameric Bence Jones proteinemia, the fifth case without proteinuria, and the fifth case involving lambda light chains.