We presented a case of acute inflammatory demyelinating polyneuropathy associated with autoimmune chronic active hepatitis (AI-CAH). This is the third case report of neuropathy in AI-CAH. A 64-year-old male with chronic liver dysfunction was admitted to the hospital because of high fever, distal weakness and sensory disturbance of all extremities, bilateral facial weakness and dysphagia. On neurologic examination, there was bilateral weakness of the upper and lower facial muscles, bulbar palsy and severe distal weakness of all extremities. The deep tendon reflexes were absent and the sensation of touch, pinprick, temperature, and vibration was impaired bilaterally symmetrically in all extremities. Serum biochemistry revealed hyperproteinemia, hypergammaglobulinemia and elevated liver enzymes. Rheumatoid factor, antinuclear antibody anti-smooth muscle antibody were positive. Serological tests for hepatitis B surface antigen and its antibody hepatitis B core antibody, and hepatitis C antibody were all negative. Serum anti-GM1, anti-GD1b, anti-GQ1b and anti-MAG antibodies were negative. Liver biopsy findings were consistent with AI-CAH with marked lymphocytic infiltration in the portal tracts. Albuminocytologic dissociation was noted in CSF. Motorconduction velocity of the median, ulnar and facial nerves were markedly reduced with temporal dispersion. No motor response was evoked in the lower extremities. Needle electromyography revealed denervation and reinnervation potentials in the arm and leg. The sural nerve biopsy showed segmental de- and re-myelination and deposition of IgG components in endoneurium. Neurological symptoms and liver dysfunction improved with corticosteroid treatment. In this case, hypergammaglobulinemia associated with an exacerbation of AI-CAH may be responsible for the acute inflammatory demyelinating neuropathy through an unknown autoimmune mechanism.