Background: Tourette syndrome (TS) is a childhood-onset neuropsychiatric diso rder that is characterized by both motor and phonic tics. One half to two thirds of children with TS experience a reduction or complete resolution of tic sympto ms during adolescence. At least one third of adults with TS have comorbid obsess ive-compulsive disorder (OCD). Objectives: To clarify the clinical course of ti c and OCD symptoms in children with TS and determine if baseline clinical measurements in childhood are associated with future symptom severity in late adolesce nce and early adulthood. Design: Prospective cohort study. Setting: Yale Child Study Center tic and OCD outpatient specialty clinic. Participants: Forty-six children with TS who received a structured clinical evaluation prior to age 14 years. Main Outcome Measures: Expert-rated tic and OCD symptom sever ity at follow-up interview an average of 7.6 years later (range, 3.8-12.8 year s). Results: Eighty-five percent of subjects reported a reduction in tic sympto ms during adolescence. Only increased tic severity in childhood was associated w ith increased tic severity at follow-up. The average age at worst-ever tic sev erity was 10.6 years. Forty-one percent of patients with TS reported at one tim e experiencing at least moderate OCD symptoms. Worst-ever OCD symptoms occurred approximately 2 years later than worst-ever tic symptoms. Increased childhood IQ was strongly associated with increased OCD severity at followup. Conclusion: Obsessive-compulsive disorder symptoms in children with TS became more severe a t a later age and were more likely to persist than tic symptoms. Background: Tourette syndrome (TS) is a childhood-onset neuropsychiatric diso rder that is characterized by both motor and phonic tics. One half to two thirds of children with TS experience a reduction or complete resolution of tic sympto ms during adolescence. At least one third of adults with TS have comorbid obsess ive-compulsive disorder (OCD). Objectives: To clarify the clinical course of ti c and OCD symptoms in children with TS and determine if baseline clinical measurements in childhood are associated with future symptom severity in late adolesce Nye and early adulthood. Design: Prospective cohort study. Setting: Yale Child Study Center tic and OCD outpatient specialty clinic. Participants: Forty-six children with TS who received a structured clinical evaluation prior to age 14 years. Main Outcome Measures: Expert- rated tic and OCD symptom sever ity at follow-up interview an average of 7.6 years later (range, 3.8-12.8 year s). Results: Eighty-five percent of subjects reported a Reduction in tic sympto ms during adolescence. Only increased tic severity in childhood was associated w ith increased tic severity at follow-up. The average age at worst-ever tic sev erity was 10.6 years. Forty-one percent of patients with TS reported at One tim e experiencing at least moderate OCD symptoms. Worst-ever OCD symptoms occurred approximately 2 years later than worst-ever tic symptoms. Increased childhood IQ was strongly associated with increased OCD severity at followup. Conclusion: Obsessive-compulsive disorder symptoms in children with TS became more severe ata later age and were more likely to persist than tic symptoms.