Since at least 2005, Mexico has confronted a severe security crisis that threatens to undermine its rule of law and democracy. An effective police response has been hindered by frustrated citizens who do not report crime, come forward with information, serve as witnesses, or support their police. This foments a vicious cycle whereby insecurity and corruption foster dissatisfaction, which yields further insecurity and corruption. Breaking this cycle requires a better understanding of why citizens are dissatisfied with their police. One view holds that discontent is due to police corruption, but a somewhat rival perspective contends that citizens are primarily concerned with security outcomes. This study uses comparative survey data from 14 major Mexican cities to test these potentially rival approaches. It finds that both corruption and security outcomes matter, but direct experience with bribery has the single largest impact on dissatisfaction with the police.