International audience The aim of this paper is to point out the relationship between the brief stage analysed as a new market of services and the crisis of the professionalism. It is based on the British example. It underlines how the brief stage has become quite critical for the client : while he has to make his choices related to design, build, manage and operate, earlier in the project, he encounters more and more difficulties to decide between the different purposes and to define the criteria of efficiency to evaluate them. These difficulties are due to different factors : a more complex demand due to increasing social differentiation , but also deep breakdowns in public policies and project financing. The spread of the model of service in the brief stage opens new opportunities to cooperate , face to the rise of risk and uncertainty. But, at the same time, it precipitates the crisis of professionalism. Its legitimacy, based on the client oriented service ideology, used to lay on the separation with the contractors (through the sequential separation between activities) and the separation with the other professions, (though the separation between the different knowledges and disciplines). But, this legitimacy is to-day threatened, under the influence of the rise of a new “ organisation model ” - with new cognitive approaches, more solving problems oriented – but also as a consequence of neo-liberal approach of economics.