This study used audiotaped chimes and a student checklist to improve the on-task behavior of three 10th-grade students with ADHD. The study took place in a high school study hall specifically for students with disabilities. The observers used a 10-second whole interval recording system to record on-task/off-task behavior within an alternating treatment experimental design. The conditions included: Baseline, Self-monitoring, and Self-monitoring with Reinforcement. Results indicate that all three participants improved their on-task behavior. Self-monitoring alone was effective in increasing the on-task behavior of two participants. Self-monitoring with reinforcement was needed to increase the on-task behavior of the third student. (Contains 3 figures.)