A case of severe neuropathy due to macro-globulinemia is reported with clinical, biochemical and electrophysiological studies. The clinical picture was that of a severe, symmetrical polyneuropathy of a sensory-motor type with increased protein in the CSF. Sedimentation rate was increased and a sharp rise was found in the globulin fractions on plasma electrophoresis. Immuno-assays of CSF showed increases of albumin, transferrin and gamma globulin. Blood chromosome studies were normal. EMG showed neuromuscular atrophy. Nerve conduction times were prolonged. These studies are compatible with a neuropathy of an allergic or metabolic nature. Macro-globulinemia of Waldenström should be considered in the differential diagnosis of obscure neuropathies.