Achieving interoperability in an e-government context is difficult. Although the benefits of enabling e-government systems to interoperate are significant, repeated failures to build working systems provide evidence that the tasks necessary to gain those benefits are poorly understood. Many governments have addressed interoperability as primarily a technical issue. However, to address the entirety of the interoperability challenge, development teams must also consider nontechnical factors that influence their efforts to meet interoperability goals. This report describes a proposed model through which to understand interoperability in the e-government context. With this model, system developers should characterize interoperability in six dimensions: Developers need to analyze e-government interoperability requirements at the technical, semantic, and organizational levels, but they should also consider the legal, political, and sociocultural issues with which the e-government system must also interoperate. This report explains some of the challenges associated with achieving interoperability in e-government systems and presents some guidance on how to address interoperability requirements, with the goal of making both policy makers and system developers aware of the depth and breadth of these challenges.