We report a 56-year-old female with chronic progressive sensory ataxic neuropathy presenting with alternating skew deviation on lateral gaze in the clinical course. She initially developed dysesthesias in the hands and feet asymmetrically, then gait disturbance developed over several months, and she was admitted to our hospital. Neurological examinations revealed profound deep sensory loss and mild superficial sensory disturbance with the absence of deep tendon reflexes, but muscular strength was completely preserved. EMG showed no evoked response of sensory nerve velocities and normal motor nerves. Sural nerve biopsy showed moderate demyelination with mild infiltration of inflammatory cells, and no vasculitis or onion bulb formation. CSF examination revealed elevation of cell counts and protein with marked intrathecal IgG synthesis and myelin basic protein, but finding of neurosyphillis. Serological examinations did not show any evidence of collagen disease, paraproteinemia, retrovirus infections or Lyme disease. Serum antiganglioside antibodies and anti-Hu antibody were negative. No evidence of malignancy was seen by radiological examinations and assays of tumor markers. In the weeks after admission, gait ataxia progressively worsened, and then she developed alternating skew deviation on lateral gaze, suggesting that the CNS was involved. No responsible lesion was detected on MRI. Corticosteroid administration improved not only the CSF findings, but also the neurologic symptoms, including the alternating skew deviation on lateral gaze. Although the disease entity was not identified, inflammatory demyelinating processes and immune-mediated mechanisms were considered to play important roles.