This paper was presented at the 25th Annual Meeting of the Society for Neuroscience, San Diego, 1995.FUNPENE, CNPqTourette syndrome is a genetic disorder characterized by chronic multiple motor and vocal tics with a fluctuating course and modulated by internal and external environmental events. Tourette syndrome is more prevalent in males than females, and is associated with behavioural disorders such as obsessive-compulsive disorder and attention deficit hyperactivity disorder. Tourette syndrome symptoms are commonly attenuated by dopaminergic antagonists and adrenergic agonists, and usually exacerbated by psychostimulants. In this paper, I propose that dysfunction centered on the nucleus accumbens represents the neurobiological basis of Tourette syndrome. Recent evidence indicates that nucleus accumbens has a micro-organization characterized by modules of distinct neurochemical and neuroanatomical features. Our model assumes that external and internal events occurring during the development of the nervous system interact with products derived from the expression of the putative gene for Tourette syndrome, thereby inducing modular changes in nucleus accumbens. The clinical presentation, associated behavioural disturbances and response to drugs would depend on the pattern of modular dysfunction.