Oral dyskinesia or orofacial dyskinesia is considered to be one of the most severe side-effects of a chronic treatment with neuroleptics or 1-dopa, although it has also been described in nontreated people. In oral or orofacial dyskinesia, involuntary spasms cause arrhythmic movements of the tongue, sometimes with protrusion and drooling, opening of the mouth, clenching of the teeth, or pursuing and retraction of the lips. Each spasm lasts seconds to a minute or two. In orofacial dyskinesia, lip smacking, chewing and tongue movements occur in a repetitive pattern interrupting speech. The pathophysiology of the orofacial dyskinesia has been still unknown. However, previous clinical observations and basic pharmacological studies have suggested that the dopaminergic receptors, especially of D1 type, play a crucial role in causing this condition. Based on this assumption, dopaminergic receptor antagonists have been introduced as medical treatments.