The wraparound process has emerged as perhaps the most frequently implemented comprehensive approach for planning and providing individualized, community-based care for children and adolescents with serious mental health conditions. Providing comprehensive care through the wraparound process necessarily requires a high level of collaboration across organization and agency boundaries. This need for significant inter-agency or "system-level" collaboration creates a complex implementation environment for wraparound. It is therefore not surprising that creating and sustaining a hospitable implementation environment has proven to be extremely challenging. For the people who are responsible for managing the inter-organizational collaboration, it is not easy to evaluate the adequacy of local system-level support for wraparound and to see exactly what kinds of supports are lacking or where system-development efforts should focus. Furthermore, as system-development strategies are put into practice, it can be difficult to assess whether or not meaningful progress is occurring. The Community Supports for Wraparound Inventory (CSWI) was developed to respond to the need for an assessment of the extent to which a community has developed system-level capacity to implement wraparound. This article reports on a study that evaluated the reliability and validity of the CSWI for use in communities implementing wraparound. Findings indicate that the CSWI shows promise as a reliable, valid and useful tool. (Contains 5 tables.)