The former regulation stated an incomplete definition under Article 1653 former Civil Code that provided the fact that in the aleatory contracts, the effects "regarding the benefits and losses for all parties, or for one or fewer parties depend on an uncertain event.
As for the aleatory contracts, in general, the evident disproportion between the benefits of the parties is a possible consequence of the aleatory nature of the contracts.
According to Article 1224 of the new Civil Code the aleatory contracts, transaction, and other contracts provided by law cannot be appealed for lesion.
The doctrine held that the legal definition of the aleatory contracts in the former regulation until 2011, under the Article 1635 of Civil Code of 1864 was not exact, because the chances of gain or looses exist, always, for all parties, and it can't be unilateral (Mazeaud, Mazeaud, Mazeaud, 1962), Lecons de droit civil, t.
Despite the fact that the vast majority of aleatory contracts concluded by the subject of law fall within the types named by the new Civil Code, it should be noted that the number of aleatory unnamed contracts is virtually unlimited.
Considering the social importance of this type of legal act, as its spread in modern society, the first of the aleatory contracts governed by the new Civil Code is the insurance contract (Articles 2199 to 2241 Civil Code of 2009).