Tics are sudden, rapid, stereotyped, recurrent, nonrythmic, brief and purposeless involuntary movements or vocalization. The characteristics of tics is that they can be suppressed for certain minutes or hours. Tic disorders are classified into three subtypes in DSM-III. They are: transient tic chronic motor or vocal tic and Tourette's disorder. These three disorders are considered to be clinical varieties of a tic spectrum. Tic disorders are male-predominant, age-dependent (most tics appear by puberty) disorders. Autosomal dominant inheritance has been suggested in Tourette's disorder. It is highly interesting and important to investigate the pathogenesis of tic symptoms because tics are thought to be in between neurological symptoms and psychiatric symptoms.