Citizen engagement plays a vital role in US environmental decision making and planning and is embedded in tradition, law, and regulation. It can lead to better decisions and more legitimacy for those decisions, as well as to developing citizenship skills. The question of what works in varied contexts has dogged both scholars and practitioners. Recent scholarship and practice has focused on integrating technical analysis and democratic deliberation – involving community members and scientists in collaborative dialogue. It is also recognized that citizen engagement needs to be responsive to stakeholder preferences and local contexts. What works in one place may not work someplace else. Key challenges include: a scarcity of attitudes and aptitudes supportive of democratic engagement; powerful private interests subsuming the common good; deep distrust of institutions; and the underutilization of knowledge about “good” practice. Additional research efforts should focus on overcoming these challenges in a variety of contexts.