As the number of children affected by obesity increases in the United States, it is necessary to intervene with preventative and intervention techniques that will enact change. Since children spend a significant portion of their time in school, it is of particular interest to target strategies during the school day. Given recommendations for the total duration and intensity of physical activity children should participate in, recess period is a means of acquiring a portion of this daily recommendation. Contingent reinforcement is a technique that is consistently used in schools to promote behavior change. One of these techniques, group contingencies, has repeatedly been shown to increase desired behavior and decrease inappropriate behavior in schools. Group contingencies have been an appealing option when working with all students during the school day because of their time and effort efficiency. In the present study, a multiple-baseline design was utilized to investigate the use of interdependent group contingencies on physical activity performance, as measured by a pedometer, during recess. Some variability existed in gender and BMI specific subgroups, in regards to the effectiveness of the intervention and continued maintenance of increased physical activity levels, following the removal of the intervention. However, the overall results support the use of an interdependent group contingency intervention to increase the amount of physical activity third, fourth and fifth grade students engaged in during the recess. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]