This study evaluated a 10-week behavior training program for parents of children with Attention-Deficit/Hyperactivity Disorder (ADHD) and also examined whether the inclusion of an intervention provided to children's classroom teachers would result in additional behavioral benefits. Parents and teachers of 30 children with ADHD were randomly assigned to the Parent Group Only or Parent Group plus Teacher conditions. Results indicate that the program is effective in improving child behavior in the home setting. More importantly, a greater reduction in children's ADHD symptoms was observed when both parents and teachers received the intervention. This suggests that the teacher component is a simple, time- and cost-effective way of increasing the beneficial effects of an ADHD parent training program.