Tourette syndrome (TS) is an inheritable, childhood-onset neurologic disorder marked by persistent multiple motor tics and at least one vocal tic. Tics are involuntary, repetitive, stereotypic movements or vocalizations that are usually sudden and rapid and often can be suppressed for short periods. The prevalence of TS is uncertain; the broad range of worldwide estimates, from 1-30 per 1,000 population, likely is the result of differences in study methodology. This report presents the first estimate of national prevalence of diagnosed TS among a national sample of U.S. children and adolescents aged 6-17 years. Based on data from the 2007 National Survey of Children's Health (NSCH), the estimated prevalence of a lifetime diagnosis of TS by parent report was 3.0 per 1,000. A diagnosis of TS was almost three times as likely for boys as girls, twice as likely for persons aged 12-17 years than for those aged 6-11 years, and twice as likely for non-Hispanic white persons than for Hispanic and non-Hispanic black persons. Among persons ever diagnosed with TS, 79% also had been diagnosed with at least one co-occurring mental health or neurodevelopmental condition. CDC sponsors efforts by the Tourette Syndrome Association to educate health-care providers and school personnel about TS to ensure earlier identification and promote appropriate medical, educational, and comprehensive behavioral interventions for children with TS and co-occurring mental health or neurodevelopmental conditions.