The subjects of this paper proves unequivocally that the excretion of lambda light chains must be considered a nephrotoxic process. It should be stressed, that although only a relatively small number of cases are known, this view is justified. According to our present knowledge, the process is irreversible and lethal. That the time required for the development of renal insufficiency is long can be established even without objective measurements. Under these circumstances it is justified to apply every available treatment that promises the reduction of the concentration of nephrotoxic substances, and their effects. A technical solution for treatment is plasma exchange. Although it is no definite therapeutic factor, if applied repeatedly the administration of drugs, - sufficient care being taken to avoid excessive load on the patient, it may prolong his life (49).