This thesis is a study of the effects of international trade on social welfare within countries. The analysis starts from the evidence that there are countries with similar economic structures, including a high level of economic openness which, however, have a very different performance on their HDI, taken as a proxy for their welfare. The cases of Chile and Venezuela in the 1990s are examined. The conclusion is that, although trade, in countries highly exposed to it, is to a great extent responsible for the evolution of national economies as a whole, the way it affects welfare depends on the intervention of the state, through the implementation of policies. The research is done within an International Political Economy (IPE) framework. Susan Strange's proposition of analyzing the questions of IPE as the work of different power structures is applied at the national level, and the effects of international trade on HDI are examined as those of a particularly strong trade structure on a welfare structure.