The authors trace the definition and challenges of "service integration," variously known over time as "collaboration," "coordination," "human services integration," and "one-stop shopping." While the common use of service integration terminology currently may seem to indicate a consensus in favor of a broad systemic reform, motivations and expectations for service integration differ significantly among different players in the service system. The authors conclude that service integration cannot be defined by a particular service model or outcome, but instead should be conceived of as an ongoing reform process. This process, when well-designed and implemented with long-term vision, can reduce duplication, strengthen communities, and improve client outcomes.