Over the past 15 years we have treated 526 patients with severe hyperkinetic movement disorders with tetrabenazine (TBZ), a monoamine-depleting and a dopamine-receptor-blocking drug. We report here the results in 400 patients with adequate follow-up. The response was rated on a scale of 1 to 5 (1 = marked improvement, 4 = no response, 5 = worsening) and was assessed initially and at the last clinic visit. The average duration of TBZ treatment was 28.9 months (+/- 31.1; range, 0.25 to 180 months). The global response rating of 1 (marked improvement) was recorded in 89.2% of 93 patients with tardive stereotypy, 83.3% of 12 with myoclonus, 82.8% of 29 with Huntington's disease, 80.5% of 82 with tardive dystonia, 79.3% of 29 with other movement disorders, 62.9% of 108 with idiopathic dystonia, and in 57.4% of 47 with Tourette's syndrome. The most common side effects included drowsiness (36.5%), parkinsonism (28.5%), depression (15.0%), insomnia (11.0%), nervousness or anxiety (10.3%), and akathisia (9.5%). The side effects were controlled with reduction in the dosage. TBZ is an effective and safe drug for the treatment of a variety of hyperkinetic movement disorders. In contrast to typical neuroleptics, TBZ has not been demonstrated to cause tardive dyskinesia.