The globalization of the economy and the crisis of the welfare state are two worldwide phenomena. In the case of developing nations, the process generate severe social difficulties. The creation of numerous poverty Non Governmental Organizations(NGOs) seem to be a promising way of adressing problems that has not been solved by agencies within the public or private sector. However, research about the concrete nature of these organizations is limited in Argentina, as well as in other developing countries. To expand the knowledge about this relevant social actor it is necessary to add to the empirical research on poverty NGOs in Latin America. This is a case study of poverty NGOs operating in one of the poorest sections of one of the largest Latin American areas, Moreno-Greater Buenos Aires. The methodological strategy, based on thhe grounded theory approach, is both inductive and qualitative. Cases are selected trough theoretical sampling procedures. The main research method used is interviewing, conducted with members at different levels of these organizations, as well as other key informants and benefitiaries of the NGOs´services. Other methods used are participant observation and analysis of available printed materials.The main findings can be sorted in two categories: empirical and theoretical. At an empirical level, the creation and consolidation of grassroots NGOs among the poor by militants inspired primarily by the Theology of Liberation and supported by the Church and State agencies was observed despite severe difficulties and fierce struggles. These new organizations are developing in a novel inter-organizational field with both vertical (hierarchical) and horizontal (network) patterns of articulation. The ongoing process of institutionalization os this sector is reflected in the NGOs´ismorphic tendencies. At a theoretical level, a conceptual framework combining old and new institutional approaches in the Sociology of Organizations in light of Structuration theory, was developed in order to analize the mergence of a novel inter-organizational field.