“…Increased serum concentra tions of fi2m are observed in cases with high cell proliferation rates: in lymphoprolifér ative disorders such as monoclonal gammopathies or leukemias, and in certain other malignancies [1,2,7,8,11,12,14,15,[22][23][24], Serum concentrations also depend on the glomerular filtration of p2m [3,4,27], and are thus affected in patients with impaired renal function. The differentiation whether an increased /?2m value is due to increased synthesis or rather to decreased glomerular filtration can be made by a par allel determination of serum creatinine [6,27], In continuation of our earlier studies [18] we were interested in the value of serum /5.,m determinations as an aid in distinguish ing between benign monoclonal gammopathy and malignant gammopathies, such as multiple myeloma and Waldenstrom's macroglobulinemia. For this purpose we com pared serum (¡.¿m levels with the degree of bone marrow infiltration by plasma cells.…”