Efficacy of Aripiprazole Versus Placebo in the Reduction of Aggressive and Aberrant Behavior in Autistic Children

Inclusion Criteria: * Meets DSM-IV, ADI-R criteria for autistic disorder. * Age 5-17 years. * Outpatients * Parent or legal guardian willing to sign informed consent. Exclusion Criteria: * Subject has been diagnosed with a psychotic disorder (such as schizophrenia) or a mood disorder, including depression or bipolar disorder (manic depression). * Subject has caused visible harm to him/herself. * Subject has an active seizure disorder or epilepsy (seizures within the past year). * Subject has an unstable medical illness, including heart disease. * Subject has experienced brain injury. * Subject has a history of diabetes. * Subject reports significant improvement of autism symptoms and behaviors to current medication or other therapies. * Subject has a history of prior treatment with Aripiprazole of 5 mg/day or higher for 6 weeks. * Subject lives in a far away area and/or does not have regular access to transportation to the clinical facility. * Subject is a pregnant female or unwilling to use acceptable contraception if sexually active.