The subjects were 20 patients with Parkinson's disease. They were aged 52 to 76 years and the duration of the disease ranged from four to 25 years (mean, 12.5 years). All the patients were receiving levodopa alone or in combination with tricyclic antidepressants, amantadine, bromocriptine, anticholinergic agents, or lisuride. Each patient received 1,000 mg of citicoline intramuscularly daily for 15 days and then 500 mg daily for 15 days. After 30 days of treatment, the scores on the Columbia rating scale improved 7.3%; rigidity was improved 18.8%; times to walk 10 m and turn over were reduced 17.5% and 37.4%; and the handwriting test scores improved 19.7%. No side effects were reported. Four patients with advanced parkinsonian symptoms and psychotic side effects received 2,000 mg of citicoline subcutaneously or intravenously for seven days. No improvements in symptoms or treatment side effects were noted.