Patients will be ages 18 to 65 and have clinically documented Tourette's syndrome or chronic motor tic disorder as defined by DSM-IV-TR (American Psychiatric Association, 2000) and evaluation of tic severity using the Yale Tic Scale (YGTS). This criterion will be established by preliminary screening in the NINDS Movement Disorders Outpatient Clinic. Structure Clinical Interview for (DSMIV SCID) will be administered to all patients to ensure that strict DSM-IV criteria for Tourette Syndrome have been met and to assess for possible comorbid psychiatric disorders.