Tic disorder including Tourette's disorder is a neurodevelopmental disorder that appears in childhood and characterized by the presence of motor and vocal tics. Childhood-onset obsessive-compulsive disorder (OCD) is suggested to be a phenomenologically and etiologically distinct subtype of OCD, bearing a close genetic relationship to tic-disorders. Tourette's disorder and OCD are comorbid in $40-75\%$ of patients initially diagnosed with either disorder. Basal ganglia and cortico-striato-thalamic circuits are implicated in the pathophysiology of both disorders and these disorders have similar clinical features. Over the past decades, the progress in research on Tourette's disorder and OCD has been extraordinary. This review describes some of important insights from these work, involving these areas : 1) clinical implication 2) genetics and epidemiology 3) brain imaging study 4) neuroche-mistry 5) pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection (PANDAS).