Accurate screening of disruptive behavior disorders such as attention-deficit/hyperactivity disorder (ADHD) and oppositional defiant disorder are a priority in elementary schools and child guidance clinics but they can be challenging because of symptom overlap with other disorders. The use of behavioral rating scales for assessing children's behavior has remained popular because of their comprehensiveness, time efficiency, and economy. One such behavior rating scale in common use in the schools is the ADD-H Comprehensive Teacher Rating Scale-Second Edition (ACTeRS-2). The ACTeRS-2 is a 24-item rating scale completed by the students' teacher. This article presents the findings of a study exploring the internal consistency, test-retest reliability, and factorial and convergent validity of teacher responses to the ACTeRS-2. Factorial validity was examined through confirmatory factor analytic methods as well as by using an inter-item absolute correlation graphing method. Decision efficiency (i.e., diagnostic accuracy) was examined using procedures described by Erford and Widiger, Hurt, Frances, Clarkin, and Gilmore. Evidence of convergent validity was provided through correlations with other tests purporting to measure disruptive behaviors, such as the Conners' Teacher Rating Scale-Revised: Short Form, Disruptive Behavior Rating Scale-Teacher Version, and the School Situations Questionnaire. (Contains 3 figures and 2 tables.)