This Article addresses the implications of broad-based participatory reforms for administrative process, with a particular focus on how participation reveals itself in different political-theoretic models of agency governance. The first section of the Article explores participation's value to agency governance. The second section of the Article presents three models of agency governance - expertocratic, pluralist, and civic republican - and discusses participation's importance to each model. The Article then posits a distinction between ordinary and constitutive agency decision-making, and explores how participation affects each for the three distinct models of agency governance. The implications of mass participation are explored in the context of citizen suit provisions to enforce environmental laws, the Environmental Impact Statement process under the National Environmental Policy Act, and sunshine laws which require meetings of multi-member agencies to be open to the public. The Article concludes by suggesting that mass participatory reforms to administrative law have adverse implications for the models of agency governance in various contexts, but are particularly deleterious for civic republican theories of administrative law. Thus, the Article suggests, de-emphasizing participation in administrative law theory and reforms may work to make agency governance more democratic.