Neuropsychiatric disorders of childhood include conditions such as autism, pervasive developmental disorder and attention deficit hyperactivity disorder. Tourette's syndrome (TS) of chronic, multiple, motor and vocal tics is a model neuropsychiatric disorder with a childhood onset and long-term, and sometimes life-long, course. Symptoms and signs change during the course of maturation, and include obsessions, compulsions, attentional difficulties and psychological responses to the disability. These clinical features reflect the interaction between genetic and environmental factors. The localization and cloning of the genetic substrate will allow for detailed study of the pathways from molecular vulnerability to clinical syndrome.