Objective: This study examines changes in severity of tics and ADHD during atomoxetine treatment in ADHD patients with Tourette syndrome (TS). Method: Subjects (7-17 years old) with ADHD ("Diagnostic and Statistical Manual of Mental Disorders, DSM-IV") and TS were randomly assigned to double-blind treatment with placebo (n = 56) or atomoxetine (0.5-1.5 mg/kg/day, n = 61) for approximately 18 weeks. Results: Atomoxetine subjects showed significantly greater improvement on ADHD symptom measures. Treatment was also associated with significantly greater reduction of tic severity on two of three measures. Significant increases were seen in mean pulse rate and rates of treatment-emergent nausea, decreased appetite, and decreased body weight. No other clinically relevant treatment differences were observed in any other vital sign, adverse event, laboratory parameter, or electrocardiographic measure. Conclusion: Atomoxetine is efficacious for treatment of ADHD and its use appears well tolerated in ADHD patients with comorbid TS. (Contains 4 tables and 1 figure.)