This study investigated whether the Barkley behavior change program was effective in changing oppositional-defiant behavior of a 12-year-old, male student. The Barkley program uses an applied behavior analysis approach with daily assessment and reinforcement. Weekly meetings were held between the student's parents and the school psychologist at which the parents were taught the procedures of the 10-step program. The study used a pretest, treatment, posttest design, and also a continuous measurement of daily behavior at school. The treatment lasted for 5 months. Results indicated statistically significant improvement in the student's behavior, and records from the daily behavioral measurements also indicated notable improvement. Observations from the student's parents and classroom teacher verified this improved behavior. (Contains 26 references.) (DB)