Patients are evaluated with the following questionnaires at ages 2-3 years and again at ages 5-9: The Autism Diagnostic Interview (ADI); The Autism Diagnostic Observation Schedule (ADOS); Assessment of cognitive functioning; Expressive and receptive language; Adaptive functioning; Measures of burden and functional assessment; The Aberrant Behavior Checklist; The Connors Rating Scale - Parent and Teacher version; and Autism Behavior Checklist