This paper discusses the Xinfang institution of petitions (letters and visits) and explores the ways in which the Chinese Communist Party regime utilizes social control mechanisms to identify, oversee, and suppress socially discontented people with grievances in the post-Mao market reform era. This public-facing institution for managing participation and rightful resistance, which aims to oversee local officials and redress mass grievances, also plays an unexpected role in social control. Unlike the social control exercised by police patrols in police states, Xinfang functions first as a ＂fire alarm＂ in this authoritarian regime; then, if necessary, as a selective ＂police patrol,＂ collecting information on discontented people with grievances, monitoring them, quelling and even preempting their protests, and referring dangerous petitioners to higher levels of government to prevent disruption in politically critical regions. This argument is supported with a detailed institutional analysis of the nationwide structure of Xinfang and several case studies of Xinfang's multi-layered response to petitioners to Beijing, during the Falun Gong incidents in 1999 and 2000 in particular. Several complementary case studies on the behavior of local petition mechanisms and statistical evidence are also analyzed.