The thesis analyses the University for All Program - ProUni - an affirmative action policy carried since 2005 by the Federal Government, in favor of black and low income students. Hence, it evaluates the ProUni implementation processes alongside three axes: its macro-structural, meso-institutional and microssocial effects - according to the perceptions of some incumbents of the Ministry of Education, several leaders of social movements engaged in this affirmative action policy, and a sample of undergraduated students benefited by ProUni scholarships in two private universities. The thesis framework is developed from theories related to social networks, based upon political participation of newtworking organizations (Scherrer-Warren), in order to give a due account for the many political, intercultural and economic processes muddling through these several movements, groups and individual actors participating in these policies and politics. The research develops both quantitative and qualitative data analysis techniques, stressing their complementary resources. The tree analytical axes of the thesis point out: i) at the macro-structural level the ways this social policy accounts for determinism and conditioning influences played by economic, cultural and political structures in Brazilian society; ii) at the mesoinstitutional level, it pinpoints the new institutionalization processes generated in two private Universities in Rio de Janeiro area, as results of ProUni implementation of 10% of scholarship in favor of low income and black students; iii) at the microssocial level it emphasizes cultural and social changes and adaptations generated among the undergraduated students and their reference groups. Hence, at the macro-structural level, ProUni is shown as a public policy developed by the Federal Government - alongside several movements of the Civil Society - aimed at improving higher education democratization in Brazil. It is also a rationalization endeavor aimed at tax deduction and philanthropy laws favoring private universities, in exchange of 10% of free enrollment cottas by black and low income students. Therefore, it stresses ProUni governance structures and its politics arrangements inside the policy cycle. At the meso-institutional dimension of analysis, the thesis finds out how ProUni plays a significant effect on democratizing the scholarship practices already developed by the Catholic University of Rio, as well as on reshaping the previous philanthropy and taxes deduction processes implemented by other private university, Castelo Branco University. At the microssocial axis, the thesis finds out the positive perceptions developed by the universities students, in relation to their academic and cultural insertion in higher education, to their increasing opportunities in enhancing new knowledge, intercultural experiences and professional qualifications required by the professional world.