This study evaluated the effects of a peer-administered positive behavioral support intervention on a school-wide problem behavior. Utilizing the differential reinforcement of incompatible behaviors method (DRl), peer monitors praised incidences of walking in order to decrease incidences of running in the hallway. A multiple baseline design across two hallway settings was used to evaluate the effect of peer monitors administering verbal praise and praise notes to students who demonstrated the desired behavior, walking. A lottery drawing in which recipients of praise notes received small prizes was conducted at the end of each week during the treatment phase. Results indicated that incidences of running significantly decreased following implementation of the peer-administered positive behavioral support intervention in both settings. In addition, a maintenance phase suggested that treatment effects were maintained when the peer-administered intervention was withdrawn in the two hallway settings. Results were socially validated by teachers who indicated that they were generally satisfied with the intervention four weeks after termination of the treatment phase. Implications for research and practice are discussed.