In this chapter, the authors theorize organizational integration by extending, elaborating, and combining various theoretical perspectives, such as structural contingency theory, organization economics, and organizational culture. The aim of this study is to provide the foundation for a holistic theory of integration that examines the different relevant facets of integration and a comprehensive set of tools – integrative devices – by which integration can be sought by those who design the organization. To this end, the authors examine the integration challenge that arises from various types of subunit interdependence – pooled, sequential, and reciprocal – and theorize which configurations of integrative devices are more likely to be effective in a given task environment. The authors close by discussing directions for future research on organizational integration.