No medications have been investigated to improve attention and executive functions in patients with Huntington's disease, despite the evidence that these cognitive domains can be abnormal even before motor symptom onset. Because cognitive symptoms are highly associated with functional disability, treatments aimed at improving cognitive functions would be of significant benefit to patients in the early stages of the disease. Atomoxetine is the ideal choice for such a trial. It has proven efficacy in adults with attention deficit hyperactivity disorder (ADHD) and it selectively targets norepinephrine and dopamine in the prefrontal cortex rather than in subcortical areas. This selectivity is an advantage for patients with HD, because motor side effects are less likely to be facilitated than with a psychostimulant. The present study is a feasibility study in which we propose to administer either 80 milligram (mg) atomoxetine for 4 weeks or placebo to 20 patients with early HD who also complain of mild cognitive symptoms. The groups will then crossover to the other condition (atomoxetine or placebo). Participants will be assessed on measures of ADHD symptoms and a sensitive battery of neuropsychological tests. Based on the shared neural circuitry in ADHD and HD, and the demonstrated effectiveness of atomoxetine on attention in adults with ADHD, improved performance on cognitive tests of attention and executive functions and on subjects' report of ADHD symptoms are expected in the atomoxetine treatment phase. No changes in motor status are predicted during the study.