A Study of the Safety and Effectiveness of Risperidone Versus Placebo for the Treatment of Conduct Disorder in Children With Mild, Moderate, or Borderline Mental Retardation

Inclusion Criteria: * Diagnosis of Conduct Disorder, Oppositional Defiant Disorder, or Disruptive Behavior Disorder not otherwise specified, by the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV), Axis I criteria (patients with conduct disorder who also meet DSM-IV criteria for Attention Deficit/Hyperactivity Disorder (AD/HD) are eligible) * total rating of \>=24 on the Nisonger Child Behavior Rating Form (N-CBRF) Conduct Problem Subscale * Diagnosis of Mild Mental Retardation, Moderate Mental Retardation or Borderline Intellectual Functioning by DSM-IV Axis II criteria (represents intelligence quotients (IQs) ranging from 35 to 84) * Vineland Adaptive Behavior Scale \<=84. Exclusion Criteria: * Diagnosis of Pervasive Development Disorder or Schizophrenia and/or Other Psychotic Disorders by DSM-IV criteria * mental impairment caused by head injury * seizure disorder currently requiring medication * history of tardive dyskinesia (a complication of neuroleptic therapy involving involuntary movements of facial muscles) or neuroleptic malignant syndrome (a rare psychotropic-drug reaction, which may be characterized by confusion, reduced consciousness, high fever or pronounced muscle stiffness) * known hypersensitivity, intolerance, or unresponsiveness to risperidone.