This document is the report of the NNI Workshop on Public Participation in Nanotechnology. The workshop was sponsored by the NSET Subcommittee and the U.S. Environmental Protection Agency as part of long-range planning efforts for the NNI, guided by thoughtful concern for the opinions and benefit of the American people. The recommendations of the public participation workshop provided guidance to the NSET Subcommittee and its Nanotechnology Public Engagement and Communications (NPEC) Working Group in the development of NNI strategic plans, and they continue to serve as a reference point for ongoing public participation activities related to the NNI. Some information in the body of the report was updated through 2008.The purpose of this workshop was to gather input on how to engage the public in nanotechnology-related issues. At this workshop, people with a wide range of interests, expertise, and diverse backgrounds in industry, academia, government, and non-governmental organizations came together with members of the public at large to share perspectives and explore ideas on how to engage the public in nanotechnology policy development and decision making. Their discussions raised important questions and provided thoughtful answers about the reasons to engage the public in policy-related decisions, about ethical issues related to public participation, and about ways to approach public participation for nanotechnology. This report summarizes the workshop discussions and the recommendations and challenges that workshop participants identified relative to implementing effective and inclusive public participation activities for nanotechnology.In 2008, as part of its ongoing commitment to public engagement in the nanotechnology policymaking processes, the NSET Subcommittee chartered the Nanotechnology Public Engagement and Communications (NPEC) working group to pursue progress on this front and make recommendations about public participation and engagement activities to the subcommittee and the Federal agencies participating in the NNI. This report from the NNI Workshop on Public Participation in Nanotechnology provides invaluable insights and guidance to the NPEC Working Group and the NSET Subcommittee as they plan ongoing NNI public outreach and engagement activities. For example, based in part on the workshop recommendations, the NSET Subcommittee organized a series of stakeholder workshops in 2009 and 2010 to guide the development of the 2011 NNI Strategic Plan and the 2011 NNI Strategy for Environmental, Health, and Safety Research.