A rare cause of polyneuropathy, first described in 1936, is the Bing-Neel syndrome. This polyneuropathy develops on the basis of a paraproteinemia. Five patients in whom the symptom constellation presented, were examined. All patients complained of motor or sensory deficiencies affecting the limbs, but had no evidence of malignant disease. Four patients had IgM paraprotein, one an IgG paraprotein in the serum. In two patients, the bone marrow revealed lymphocytic infiltration in the sense of an immunocytoma, in one other patient, a plasmacytoma was detected in the bone marrow. Three patients were treated in accordance with the Knospe regimen, the patient with the plasmocytoma with the Alexanian regimen. In one case satisfactory regression of the symptoms was observed, in the other two cases a moderate improvement occurred.