Atypical antipsychotics are emerging as the first-line pharmacologic treatment for irritability (i.e., aggression, self-injurious behavior, and severe tantrums) in children and adolescents with autistic and other pervasive developmental disorders. Results from placebo-controlled and open-label studies of clozapine, risperidone, olanzapine, quetiapine, ziprasidone, and aripiprazole in this subject population are reviewed. Additional placebo-controlled trials and studies of longer-term safety and tolerability are needed.