Tardive dyskinesia (TD) is a frequently occurring side effect of treatment with neuroleptic antipsychotic drugs. TD is a persistent and often irreversible syndrome characterized by abnormal movements, including lingual and orofacial dyskinesia, grimacing, tics, choreic movements of the limbs and trunk, and athetosis and dystonia. In some patients the muscles of respiration and speech may also be involved. There is no established treatment for TD.