Very recently it was reported that the amyloid associated with chronic hemodialysis contains, as a major component, a new form of amyloid fibril protein which is homologous to beta 2-microglobulin. As beta 2-microglobulin has a molecular weight of 11,600 daltons, investigations were carried out to see whether or not this protein would be handled differently by hemodialysis and hemofiltration, because the latter method especially is capable of eliminating solutes with such a high molecular weight. The results clearly indicate that hemofiltration removes substantial amounts of beta 2-microglobulin (about 190 mg per treatment, which represents 80% of daily production). It remains to be clarified whether or not hemofiltration is therefore superior to hemodialysis with regard to amyloid deposit formation.