This article has focused on TS, and the relationship between TS and OCD has been addressed from different perspectives. In patients who have OCD, the presence of TS seems to have some impact in the clinical manifestation of OCD symptoms. One of the main features of tic-related OCD is the frequent presence of sensory phenomena preceding the compulsions, in the absence of obsessions. Genetic epidemiologic studies provide consistent evidence for the association between TS and OCD. Although no major loci have been identified so far, family and segregation analysis studies support the assumption that genes play a major role in the etiology of TS and related disorders. Genes interact with environmental factors,which can modulate the expression of TS or OCD and determine the onset of these disorders. Neuroimaging studies suggest that the pathophysiology of TS encompasses projections of primary, secondary, and somato sensory cortex to the putamen, dorsolateral caudate nucleus, and globus pallidus,whereas the pathophysiology of OCD involves more ventral structures,such as orbitofrontal-caudate-thalamic-cortical areas. Current treatment strategies for TS include education, behavioral therapy, pharmacotherapy,and support from patients associations. Alfa-adrenergic agents such as guanfacine and clonidine are first-choice treatments for TS; typical antipsychotics are more effective but are troublesome because of their long-term side-effect profiles. For comorbid TS plus OCD, each condition should be treated with its respective first-line option. Nonetheless, for patients who have tic-related OCD who are unresponsive to monotherapy with serotonin reuptake inhibitors, augmentation of serotonin reuptake inhibitors with atypical antipsychotics may be of benefit. Despite important advances, re-search is needed to clarify further the biologic and behavioral aspects of TS and its relationship with the frequently associated conditions, with particular attention to their management and prognosis.