This article deals with the evolution of the relationship between, on the one hand, the first two generations of human rights (i.e. civil and political ones, and economic, social and cultural ones) and, on the other hand, negative and positive duties of States. After a deep analysis of the origins of the first two generations of human rights, both within the United Nations and in the regional international organizations, such as the Council of Europe, the Organization of American States and the African Union, this paper identifies the elements that have weakened, over the years, the traditional difference between the first two generations of human rights, i.e. the importance of mechanisms of protection associated to each of those generations and, most of all, case-law coming from the same mechanisms. In particular, this paper underlines the importance of the doctrine of positive obligations.