An ABAB reversal design with matched placebo was employed to assess the acetylcholine precursor, deanol, in the treatment of tardive dyskinesia. Oral dyskinesia was monitored by electromyography in four patients with tardive dyskinesia. A battery of psychological rating scales was also utilized to determine effects of deanol on psychological functioning. Improvement ranged from 35 to 70% dyskinetic symptom reduction in three patients given deanol. The decrease in symptomatology, however, did not reach the level of oral EMG activity observed in a normal control subject. Psychological functioning was generally unaffected, but slight improvement was seen in two subjects.