In this article, the authors report the psychometric properties of a parent-completed rating scale based on the criteria for oppositional defiant disorder (ODD) in the "Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition-Text Revision" ("DSM-IV-TR"). Mothers of 294 boys and 48 girls with attention-deficit/hyperactivity disorder (ADHD) and 53 boys and 45 girls without behavior problems completed the Oppositional Defiant Disorder Rating Scale (ODDRS). Fathers of 44 boys with ADHD also completed the scale, and 71 mothers of boys with ADHD provided 1-year test-retest data. The ODDRS had high internal consistency, high interrater reliability, and moderate 1-year test-retest reliability. The scale had one principal component and correlated as expected with related subscales from the "Child Behavior Checklist" and with overreactive parenting. Scores were not significantly correlated with parent or child age or with socioeconomic status. The strong psychometric properties indicate that this measure holds considerable promise for briefly assessing ODD in a manner consistent with the "DSM-IV-TR."