Drug-induced tardive dyskinesia, an irreversible involuntary movement disorder caused by neuroleptic drugs, may reflect cholinergic hypofunction in the corpus striatum. Therapeutic results have been reported in trials of choline and lecithin, nutritional substrates which may enhance cholinergic neurotransmission. Lecithin's effects on dyskinetic symptoms were examined in 50 male patients in a double-blind, placebo-controlled trial. Patients were randomly assigned to treatment or control groups; 31 patients were retained in the analytic cohort. Experimental patients were treated with 60 gm/day lecithin (55% phosphatidyl choline) for 11 days. Symptom frequency was rated from videotapes made at baseline, 3 and 11 days of treatment, and 1 week follow-up.