This study was withdrawn due to competing research interests and slow recruitment.

The main objective of this exploratory 8 week pilot study is to evaluate the safety and efficacy of buspirone for the treatment of anxiety in youth (ages 6-17 years) with autism spectrum disorders. The study results will be used to generate hypotheses for a larger randomized controlled clinical trial with explicit hypotheses and sufficient statistical power.

Inclusion Criteria:

• Male or female participants between 6 and 17 years of age.
• Fulfills diagnosis of autism spectrum disorders by meeting DSM-IV-TR PDD diagnostic criteria of autistic disorder, Asperger's disorder, or PDD-NOS as established by clinical diagnostic interview.
• Participants with a score of ≥60 on the Anxiety/Depression subscale of Child Behavior Checklist (CBCL) and CGI-Anxiety severity of ≥4.
• Subjects can be on psychotropic drugs if they have been on the medication for at least 4 weeks prior to initiating study treatment and if they are on a stable dose.
• Subjects with disruptive behavior disorders, mood, or psychosis will be allowed to participate in the study provided they do not meet any exclusionary criteria.

Exclusion Criteria:

• Mental retardation (I.Q. <70)
• DSM-IV-TR PDD diagnosis of Rett's disorder, and childhood disintegrative disorder.
• History of active seizure disorder (EEG suggestive of seizure activity and/or history of seizure in last 1 month).
• Subjects with a medical condition or treatment that will either jeopardize subject safety or affect the scientific merit of the study, including: pregnant or nursing females, organic brain disorders, uncorrected hypothyroidism or hyperthyroidism, clinically significant abnormalities on ECG (e.g. QT prolongation, arrhythmia), history of renal or hepatic impairment.
• Clinically unstable psychiatric conditions or judged to be at serious suicidal risk.
• History of substance abuse (except nicotine of caffeine) within past 3 months or urine drug screen positive for substances of abuse.
• Any other concomitant medication with primary central nervous system activity other than stable regimens for >2 weeks.
• A non-responder or history of intolerance to buspirone, after treatment at an adequate dose and duration as determined by the clinician.