Social policy in Latin America has traditionally involved programs for powerful formal-sector workers. In the past decade, however, social programs for historically under-organized informal-sector workers, who comprise about half of the workforce in the region, have been growing significantly. Cash transfers, greater access to health care, and pensions for informal workers represent fundamental social policy innovations, which I will explore through a comparative analysis of Argentina, Brazil, Mexico, and Chile. Despite the growing importance of benefits for informal workers, recent scholarship on social policy in Latin America has focused predominantly on the fate of programs for formal-sector workers and has presented social policy as heading in one direction, that of privatization and scaling back of public commitments. My project seeks to recast our understanding of the evolution of social policy since the beginning of market-oriented reforms by extending the analysis to include also programs for informal workers. To explain (a) why benefits are being expanded for informal workers, (b) the overall patterns of social policy, and (c) major contrasts among countries, I focus on two factors. The first is the capacity of informal workers to participate in policymaking, specifically whether informal workers are organized and have formed alliances with labor unions. The second factor relates to the way in which policy initiatives for informal workers interact with pre-existing formal workers' programs. Through comparing these two dimensions of policy formation, I expect to uncover fundamental contrasts in these countries. Although this research involves an ambitious comparison of four countries, with the case of Chile relying only on secondary sources, I am convinced that my prior research in social policy has prepared me well to carry out this project.