The primary purpose of this study is to evaluate the tolerability and effectiveness of atomoxetine in the treatment of attention problems, hyperactivity, and impulsivity in children with ASD, and secondarily, to evaluate the possible response to atomoxetine on the core symptoms of ASD

Inclusion Criteria:

• Male and female outpatients between the ages of at least 6 years of age and not more than 17 years of age at visit 1
• Autistic Spectrum Disorder (DSM-IV TR) diagnosis of Autistic disorder or Asperger syndrome or PDDNOS
• Clinically significant symptoms of ADHD (i.e. inattention, impulsiveness, and hyperactivity) that have been present for at least six months (for subjects older than 8 years, the onset of symptoms must be before the age of 7 years)
• Medication-free for at least two weeks for all psychotropic medications (four weeks for fluoxetine or depot-neuroleptics)
• Patients must also be able to swallow capsules

Exclusion Criteria:

• Patients who weigh less than 20 kg or greater than 60 kg at visit 2
• DSM-IV TR diagnosis of a Pervasive Developmental Disorder other than Autistic Disorder, PDD-NOS, Asperger's Disorder (e.g. Rett's Disorder, Childhood Disintegrative Disorder)
• Patients who have a history of Bipolar I or II disorder, schizophrenia, psychosis
• Patients who have a current diagnosis of Major Depression (with or without psychotic features), PTSD
• Patients with a history of any seizure disorder (other than febrile seizures) or patients who have taken (or are currently taking) anticonvulsants for seizure control