In an attempt to promote service delivery integration and improve interorganizational collaboration, many recent human service delivery initiatives have included the development of interorganizational alliances such as coalitions and coordinating councils. Despite their popularity, little is known about how these alliances influence interorganizational collaboration, specifically the extent to which they alter the interactions among human service delivery organizations. The present study examined the interorganizational interactions, specifically the exchange relationships, within one county that was implementing two interorganizational alliances--a countywide coordinating council and interagency service delivery teams. Membership on both alliances was associated with broader interorganizational exchange networks. Organizations involved in a coordinating council were more likely to be included in client, information, and resource exchanges, and participate in joint ventures with a broader range of organizations. Providers involved in interagency teams also exchanged clients and information with a broader sector of service delivery organizations than nonparticipating providers. Observational data suggested that both alliances created structures and processes intended to facilitate interorganizational exchanges. Together, these results suggest that the development of opportunities for and encouragement of staff and leader involvement in these types of alliances may be an important part of our attempt to create a more integrated social service delivery system. The implications of these findings for researchers and practitioners are discussed.