OBJECTIVE:To review the clinical trials investigating the efficacy and safety of risperidone in the treatment of children with autism spectrum disorder (ASD). DATA SOURCES:Searches of MEDLINE/PubMed (1992-February 2006) were conducted, as well as an extensive manual review of journals, using the key words autism and risperidone. STUDY SELECTION AND DATA EXTRACTION:Only double-blind, placebo-controlled trials were included for review. DATA SYNTHESIS:ASD is the most common of the pervasive developmental disorders. The main characteristics (core symptoms) of autism are impairment in social skills, problems communicating, and stereotypical movements. Behavioral manifestations or maladaptive behaviors include aggression, irritability, hyperactivity, inattention, impulsivity, tantrums, and self-injurious behavior. CONCLUSIONS:Based on the data examined, risperidone appears efficacious and safe for treating certain behavioral aspects of autism including irritability, aggression, hyperactivity, and stereotypy. It does not appear to be as effective for the treatment of the core symptoms of autism.