This paper refers to an area of law which, due to its daintiness and relevance, calls the attention of those who study Private International Law. I am referring to contractual obligations. This paper aims at establishing minimum basis for legislative harmonization on contracts within the MERCOSUR. I am aware of the risks one assumes when analyzing foreign law. Notwithstanding, I face comparative law having set aside national prejudice and aiming to perfect our own institutions and find new formulas more fit to regulate human life.