Fifty years after he wrote "Pedagogy of the Oppressed" (1970), Brazilian educator Paulo Freire's work is as relevant as ever. But while many of Freire's ideas are well known in the United States, there is limited research on their application in social movement settings, a practice commonly known as "popular education". This comparative case study draws on Freire's theory of popular education to analyze two U.S.-based grassroots education programs, one with low-income residents in the Tenderloin neighborhood of San Francisco and one with front-line hospital and public school employees on the East Coast. Through six months of participant observation and over 50 interviews with facilitators and participants, the study finds that the two programs carved out spaces that were relatively independent from union and non-profit hierarchies, which enabled them to apply popular education's radically democratic principles within their organizing work and larger social struggles. These findings point to the possibility that popular education can offer participants not only knowledge and skills but also--and perhaps more importantly--strengthened "connections" across divisions, "confidence" that they can make change, and the "courage" to organize. The dissertation also expands on commonly understood meanings of "critical consciousness," arguing that what moves people to action may be not only their intellectual understanding of power, but also an increased solidarity that gives them an awareness of their collective historical agency. Finally, the study identifies tensions in the programs, for example related to funding constraints, that at times interfered with facilitators' abilities to apply the radical principles of popular education. These findings speak to the value of a reflective practice on the part of practitioners, and highlight the ongoing significance of Freirean popular education in U.S. social movement contexts. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]