Communities Mobilizing for Change on Alcohol (CMCA) is a community-organizing program designed to reduce teens’ (13 to 20 years of age) access to alcohol by changing community policies and practices. CMCA seeks both to limit youths’ access to alcohol and to communicate a clear message to the community that underage drinking is inappropriate and unacceptable. It employs a range of social-organizing techniques to address legal, institutional, social, and health issues related to underage drinking. The goals of these organizing efforts are to eliminate illegal alcohol sales to minors, obstruct the provision of alcohol to youth, and ultimately reduce alcohol use by teens. The program involves community members in seeking and achieving changes in local public policies and the practices of community institutions that can affect youths’ access to alcohol.