The U.S. National Assessment of the Potential Consequences of Climate Variability and Change was a federally coordinated nationwide effort that involved thousands of experts and stakeholders. To draw lessons from this effort, the 10 authors of this paper, half of whom were not involved in the Assessment, developed and administered an extensive survey, prepared a series of working papers, and conducted an invitational workshop in Washington, DC, on April 29, 2004. Considering all these sources, the authors conclude that the Assessment was largely successful in implementing its basic design of distributed stakeholder involvement and in achieving its basic objectives. Future assessments could be significantly improved if greater attention were devoted to developing a collective understanding of objectives, preparing guidance materials and providing training for assessment participants, developing a budgeting mechanism which would allow greater freedom in allocating resources across various assessment activities, and creating an environment in which assessments were part of an ongoing process.