The « transaction costs economics » is an appealing theory because it keeps the neo-classical theory of the firm up to date, thanks to the more recent and well admitted «bounded rationality». But it has the drawback to be in contradiction with what occurs within industrial organizations confronted with the search for reactivity. Indeed, observations show up a plurality of partners closely involved in production and innovation activities within the firm, who keep their specific identities despite the intensity and the recurrence of the relationships that should, according to Williamson, lead to the integration. In the same way, these production and innovation activities under reactivity requirements attest some collective and constructed lear- ning and decison marking processes that are also in contradiction with a hierarchical and centralized adaptation process on which the transaction costs economics relies too. That is why, I propose to substitute the transaction investments for the transaction costs principle, so as to legitimate organizational transactions as a keystone of the adaptation of the firm confronted with uncertainty and emergency constaints.