This article concentrates particularly on non-governmental organizations (NGO's) which constitute the third sector. It deals with the origins and evolution of NGO's in the world and in Brazil, and discusses their relations to the State and to international financial agencies, and their role in the core of civil society.The article focus on the perspective of the emergence of the third sector, which believes in pluralistic actions as a way of facing great questions, such as urban violence. Viva Rio movement is a relevant example, described in this article, of this articulation between different social agents.Origens e evolução das ONG. Relações com o Estado e agências financiadoras internacionais. Movimento Viva Rio.