A 26-year-old female developed mental deterioration, general convulsion, cataract and spastic gait in order since her entrance into elementary school. A diagnosis of cerebrotendinous xanthomatosis (CTX) was made because of hypercholestanolemia. At the time of admission, cataract, a mild thickening of Achilles tendons, mental deterioration, spastic paraparesis, truncal ataxia, and bradykinesia were noted. Bilateral slowing of 2 to 7 Hz was recorded in EEG, and brain CT and MRI revealed mild cerebellar atrophy. HVA and 5-HIAA levels in CSF were low. Oral administration of chenodeoxycholic acid, 300 mg per day, resulted in improvement of bradykinesia and EEG abnormality, increase of HVA and 5-HIAA levels in CSF, and decrease of serum cholesterol level in two weeks. Bradykinesia observed in the present case is a rare clinical finding of CTX, and the improvement of bradykinesia soon after the treatment with chenodeoxycholic acid has not been reported yet. This case is important for elucidating the mechanism of neurological disorders in CTX.