Autistic disorder (AD) may be associated with dysfunctional behaviors which significantly interfere with a child's functioning. Risperidone has been described as having salutary effects as an adjunctive pharmacotherapy in adult and pediatric patients with AD. The purpose of this 8-week, open-label study was to examine the effectiveness and tolerability of risperidone monotherapy in young patients with AD. Doses of risperidone were to be started at 0.25 mg qhs and were titrated to maximize clinical efficacy. Six patients (ages 5 to 9 years) were enrolled in this protocol, and all completed it. After 8 weeks of treatment, with a mean risperidone dose of 1.1 mg, improvement in symptomatology was demonstrated by reduced scores on both the Children's Psychiatric Rating Scale (p < .005) and the Clinical Global Impressions Scale (p < .001). The most common side effect were weight gain and sedation. This study provides preliminary evidence that risperidone monotherapy may be safe and effective in ameliorating dysfunctional behaviors in children with AD.