The effect of sodium valproate 1200 mg daily on the disability of Parkinsonism and on levodopa-induced dyskinesia was assessed in a double-blind crossover trial with matched placebo in 12 patients with Parkinson's disease. No objective change in the severity of Parkinsonism or dyskinesias was noted. However, six out of nine patients who completed the trial noted a slight to moderate improvement in their dyskinesias with no change in their Parkinsonism. Excess salivation improved in four subjects on sodium valproate.