This study examined the effects of a function-based intervention implemented with a student, Shawn, who had attention-deficit/hyperactivity disorder, internalizing behavioral problems, and a speech and language impairment. Shawn attended a fourth-grade classroom in a self-contained school that served students with emotional and behavioral disorders. During language and math classes, Shawn exhibited high rates of off-task behavior. His teacher viewed these behaviors as disruptive, creating lost instructional time for all students. Functional assessment data indicated that Shawn's off-task behavior was maintained by attention (positive reinforcement) and escape from tasks (negative reinforcement). A function-based intervention including a communication system, a self-monitoring component, and extinction resulted in improvements in Shawn's behavior. The classroom teachers and Shawn rated the intervention favorably. Limitations and directions for future research are offered. (Contains 2 figures.)