Over the last decade, at least 42 U.S. cities have elected to pursue sustainable cities programs to improve their livability. Some programs are broad, involving smart growth efforts, and others are narrowly targeted, including bicycle ridership and pesticide-reduction programs. A recurring theme in these cities is the role of public participation in shaping and implementing these programs. In cities where the sustainable cities idea first emerged in local grassroots organizations, such as Seattle, these programs owe their existence to public involvement. Other cities have taken a top-down approach, treating sustainability as a matter for experts rather than ordinary citizens. Civic engagement is manifest both in the development of the sustainability program and as an explicit goal of the sustainability program. This article examines the role of civic engagement in these programs and defines a research agenda by identifying hypotheses about the importance of public involvement in sustainable cities programs.