To better understand the relationships between IS organizations and their associated client business (line) organizations, we build and test a theoretical model of the management of these relationships. This model originates in the political economy framework of organizational analysis, and couples two streams of theories: transaction cost analysis and resource dependency analysis. Additionally, elements of social contract theory are used to emphasize the long-term, relational aspect of the IS-line relationship. From these frameworks, two dimensions of the IS-business relationship are proposed: Sustainability and Influence. These constructs are conceptualized separately for each participant, emphasizing the disparate perspectives held by IS and the line. The model is validated with a field study of 121 IS-line relationships, in which the reliability and validity of the model is established in a confirmatory factor analytic approach.