This study's aim was to estimate the prevalence and describe the clinical characteristics of Tourette syndrome (TS) in 13-14-year-old schoolchildren attending mainstream secondary schools. A three-stage ascertainment procedure was used to identify those who had TS. First, all 1012 Year 9 pupils were screened for tics using validated self-report questionnaires, which were completed by parents, teachers, and pupils. Data were available from at least one informant for 918 (90.7%) subjects. Tics were identified in 189 (18.7%) pupils. Second, families were contacted and a semistructured interview was carried out to determine whether they had TS. Finally, to ensure that the diagnosis of TS was correct, all those assessed as having TS were systematically assessed by an expert clinician in the field of TS. Seven young people were identified as fulfilling the criteria for TS, giving a minimum prevalence rate amongst 13-14-year-olds of 0.76% (95% CI 0.31 to 1.57) and a more realistic estimate of 1.85% (95% CI 1.00 to 2.95). Behavioural problems, in particular hyperkinetic disorder, were frequently associated with the TS group. These findings lend further support to the contention that the prevalence of TS in the community has hitherto been underestimated, though the symptoms may be generally milder than cases of TS presenting to clinics. This study supports the need for vigilance for TS in school-age children in primary care and in educational settings, so that children with this potentially serious disorder can be identified and assessed and effective management packages can be formulated to address their needs, when necessary.