Objective: To assess the utility and tolerability of higher than standard atomoxetine doses to treat attention-deficit/hyperactivity disorder (ADHD). Method: Two randomized, double-blind trials of atomoxetine nonresponders ages 6 to 16 years were conducted comparing continued treatment with same-dose atomoxetine to treatment using greater than standard efficacious doses (study 1: up to 3.0 mg x kg[superscript -1] x day [superscript -1]; study 2: up to 2.4 mg x kg[superscript -1] x day[superscript -1]. Results: The primary outcome measure for both studies was mean ADHD Rating Scale (ADHD RS) total score. For study 1 (N = 122), decreases in ADHD RS total scores were not significantly different between treatment groups (mean change [SD]: continued same dose, -8.9 [11.2]; high dose, -9.8 [13.1]; p = 0.595). Likewise, for study 2 (N =125), treatment groups did not differ (mean change [SD]: continued same dose, -6.2 [12.2]; high dose, -8.9 [10.0], p = 0.110). Tolerability was not significantly different between the continued same-dose and high-dose groups. Conclusions: These studies provide evidence that current dose recommendations are appropriate for most patients,suggesting no systematic advantage to increasing atomoxetine doses beyond current guidelines. In both studies, continued treatment, whether at a higher dose or the previous dose, was associated with improved outcomes in patients who demonstrated incomplete/inadequate response to acute ADD treatment, although without a placebo arm, we cannot rule out the possibility that expectancy played a role in symptom improvement. (Contains 2 figures and 4 tables.)