Abstract: Interagency coordination is one of the great challenges of modern governance. This Report, prepared for the Administrative Conference of the United States (ACUS), highlights the challenges presented by fragmented agency responsibilities. Rather than oppose all agency fragmentation, the Report highlights instances when it presents governance problems and describes the variety of tools that Congress, the President, and agencies may use to manage coordination challenges more effectively. These tools include agency interaction requirements, formal interagency agreements, and joint policymaking. This Report also assesses the relative strengths and weaknesses of these coordination tools using the normative criteria of efficiency, effectiveness, and accountability, and it concludes that the benefits of coordination will frequently be substantial. To varying extents, these instruments can reduce regulatory costs for both government and the private sector, improve expertise, and ameliorate the risk of bureaucratic drift without compromising transparency. Coordination can also help to preserve the functional benefits of shared or overlapping authority, such as promoting interagency competition and accountability, while minimizing dysfunctions like discordant policy. Building on the existing literature, and past proposals of organizations like ACUS, the Report recommends a comprehensive executive branch effort to promote stronger interagency coordination and improve coordination instruments. The Report also recommends some more targeted reforms designed to promote coordination and its benefits, including development of agency policies on coordination, sharing of best practices, ex post evaluation of at least a subset of coordination processes, and tracking of outcomes and costs. These reforms could be adopted in a new Executive Order on agency coordination; added as amendments to existing Executive Order 12866 or 13563; adopted as part of the Office and Mangement and Budget’s implementation of the Government Performance and Results Act; or prescribed by Congress via statute. Agencies might also voluntarily adopt a number of these reforms. This Consultants' Report served as a background for ACUS Recommendation 2012-5, "Improving Coordination of Related Agency Responsibilities," adopted on June 15, 2012.