An old antimalarial drug quinacrine is one of the compounds that can inhibit the accumulation of pathogenic prion protein in cultured neuroblastoma cells. Here we report the result of a clinical trial of quinacrine administration to a patient with Creutzfeldt-Jakob disease (CJD). A 37-year-old woman was admitted to our hospital for ataxic gait, hallucination and dementia in August 2001. As a past history she had received an operation for cerebellar astrocytoma and had a cadaveric dura mater graft at 14 years old. After hospitalization she showed signs of anxiety, stimulus-sensitive myoclonus, decorticate rigidity, then deteriorated pursuit eye movement and voluntary limb movement. The ethics committee of Dokkyo University hospital approved this treatment, and the family of the subject was fully informed as to the nature and purpose of the treatment and gave their consent. One week after the administration of 300 mg/day of quinacrine, voluntary limb movement and pursuit eye movement appeared. There was PSD on EEG, but one week after administration of the quinacrine, PSD disappeared, and a theta wave was recognized as the basic activity on the EEG. But her symptoms deteriorated again after 3 weeks, and PSD appeared. Liver dysfunction developed 2 months after administration, and the administration of quinacrine had to be stopped. Quinacrine was administrated to a CJD patient who received a cadaveric dura mater graft and developed CJD 23 years later. The symptoms of the patient were transiently improved with the disappearance of PSD on EEG. Although the mechanism of quinacrine for the central nervous system is still unclear, this case suggests that quinacrine may be clinically one possible drug for treating CJD.