Behavior support in schools is increasingly viewed as a three-tier prevention effort in which "universal" interventions are used for primary prevention, "targeted" interventions are used for secondary prevention, and "intensive" interventions are used for tertiary prevention. A growing body of research has demonstrated the effectiveness of targeted interventions in decreasing the frequency of problem behaviors. The Check In-Check Out Program (CICO) is becoming a recognized targeted intervention. The present study examines if there is a functional relation between the implementation of CICO and a reduction in problem behaviors. Results indicate that implementation of CICO with four elementary school-age boys was functionally related to a reduction in problem behavior. Clinical and conceptual implications of these results, methodological limitations, and future research directions are reviewed. (Contains 4 tables and 1 figure.)