The topic of the legal framework for the negotiations and the relevant precontractual liability is particularly interesting from a comparative perspective: first, because of the involvement, besides the rules of law, of historical, cultural and economic values representing the matrix of a legal system; second, because this area of law is still typified by differences between the civil law family and the common law one. While the dominant paradigm of the first one is the duty of good faith - which has influenced even recent codifications, for example the new Chinese civil code - the second one, in particular the English legal system, persists in the traditional aleatory view of negotiations as well as in preserving the freedom not to contract and relying upon the so called “piecemeal approach” in order to provide for the negotiation-period. Moreover, while the English legal system maintains a clear disfavour towards any precontractual duty of good faith, a more mitigated approach is adopted by the US legal system, whereby, on one side, the aleatory view of negotiations is affirmed but, on the other, the concept of “reliance” has been expanded to protect the precontractual expectations of the parties, and the Courts tend to enforce the duty to negotiate in good faith if it is undertaken through an agreement between the parties. However, the absence of clear guidelines and the inconsistencies within the case law raised uncertainties and enhanced the transaction costs under both models. Within the field of international contracts, the above-described dichotomy and the need to grant business parties with a proper legal framework for the precontractual period is particularly enhanced due to peculiar features of such context. This induced, on one side, the development of rules of law aimed at governing the negotiations and, on the other side, the adoption of specific legal tools by the international business community, in particular the so-called letters of intent. However, unless parties specifically address the typical issues dealing with precontractual negotiations, it will be up to Arbitral Tribunals (or to national Courts) to intervene in order to solve them. Such phenomenon, therefore, determines an ongoing interaction among different models and formants, generating a unique context of analysis from the comparative point of view.