Successful implementation of innovations is central to social service organizationsí effectiveness and improvement of services to clients. Yet administrators face a host of challenges and implementation failures are common. This paper discusses the nature of the innovation implementation as inherently dynamic, endogenous to the organization, and constrained by conditions of bounded rationality. Several system dynamics models of innovation implementation are reviewed from manufacturing, health, and human services in terms of their appropriateness and evidence base for social services. Recommendations for practice and a research agenda offered.