Gilles de la Tourette syndrome is a neurodevelopmental disorder consisting of multiple motor and one or more vocal/phonic tics. Tourette's syndrome is increasingly recognized as a common neuropsychiatric disorder usually diagnosed in early childhood, and comorbid neuropsychiatric disorders occur in approximately 90% of patients; the most common of these are attention deficit hyperactivity disorder and obsessive-compulsive disorder. Depression is also common, with a lifetime risk of 10% of patients. Moreover, a high prevalence of personality disorders has been reported in preliminary investigations on Tourette's syndrome populations. This paper provides an updated review of the literature on the multifaceted phenotype of Tourette's syndrome, with special attention to the behavioral problems and the relationship between Tourette's syndrome and comorbid neuropsychiatric conditions. The issue of whether Tourette's syndrome should still be considered as a unitary nosological entity is also addressed.