Phase IV Long-term Maintenance Study of Aripiprazole in the Treatment of Irritability Associated With Autistic Disorder

Key Inclusion Criteria: * Male or female children or adolescents, 6 to 17 years of age, inclusive, at the time of the baseline visit * Meets current diagnostic criteria of the Diagnostic and Statistical Manual-of Mental Disorders IV-Text Revised for autistic disorder and displays behaviors such as tantrums, aggression, self-injurious behavior, or a combination of these problems. Diagnosis of autistic disorder will be confirmed by the Autism Diagnostic Interview-Revised. * Participant or designated guardian or caregiver is able to comprehend and satisfactorily comply with the protocol requirements, in the opinion of the investigator. * Demonstrates behaviors such as tantrums, aggression, or self-injury or a combination of these problems * An Aberrant Behavior Checklist Irritability subscale score ≥18 AND a Clinical Global Impressions Severity score ≥4 at the Screening and Baseline Visits. * Mental age of at least 24 months Key Exclusion Criteria: * Treatment resistant to neuroleptic medication, based on lack of therapeutic response to 2 different neuroleptics after treatment for at least 3 weeks each. * Previous treatment with aripiprazole for at least 3 weeks duration at an adequate daily dose, without demonstrating a clinically meaningful response. * Lifetime diagnosis of bipolar disorder, psychosis, or schizophrenia, or a current diagnosis of major depressive disorder * Diagnosis of Pervasive Developmental Disorder-Not Otherwise Specified, Asperger's Syndrome, Rett's Syndrome, childhood disintegrative disorder, or Fragile X Syndrome * History of neuroleptic malignant syndrome * At significant risk for suicide based on history or routine psychiatric status examination * A seizure within the past year * History of severe head trauma or stroke * History or current evidence of any unstable medical conditions that would expose the patient to undue risk of a significant adverse event or interfere with assessments of safety or efficacy during the course of the trial * Weight lower than 15 kg * Known allergy or hypersensitivity to aripiprazole or other dihidrocarbostyrils * History of a clinically significant low white blood cell count or a drug-induced leukopenia/neutropenia * Any other medically significant abnormal laboratory test or vital sign result or electrocardiogram finding