New pyroglobulin variants were found in a patient with a typical plasma cell leukemia. One was found in the urine and proved to be a variant of Bence-Jones’ protein with a molecular weight of approximately 68,000. The other was found in the serum and appears to be the myeloma protein of IgD. Furthermore, an ultrastructural study disclosed myeloma cells in both peripheral blood and bone marrow to have cytoplasmic fibrils which might be unique for plasma cell leukemi