Argentina, Brazil, Paraguay and Uruguay subscribed Asunción’ s Treaty that gave origin to the MERCOSUR (Market Common of the South), in 1991.
This process of regional integration noticed for central objective to create a common space without borders, inside of which people, capital and goods can circulate freely. To such effect it imposed like instrumental objective, the international legislation to prevent that the national legislations blocked this goal.

The Consumer’s Law is a key piece of this harmonization; nevertheless, the advances that have taken place in the matter have been scarce.
This work points out the historical evolution of the integration in the MERCOSUR in relationship to the Consumer’s Law. Later on, we take an aspect of this normative system, particularly, the fundamental concepts, to the effects with the hope of capering to be able to show differences and similarities. 

We denominate fundamental concepts of the Consumer’s Law to those that serve as the basis for the construction of the theoretical corpus on the matter; namely the concept of: consumer, supplier, consumption relationship and goods. To conclude, we will try to prove that, at the present time, the lack of a common regulation in the MERCOSUR is a consequence, fundamentally, of the absence of any real political will, rather than to substantial differences in the vision of the member States on this matter.