Among these “bridging institutions”, start-up firms have recently been attracting particular attention. Indeed, in a number of European countries, universities, national research institutions and even R&D-based multinational companies are being encouraged to establish “incubators”, in order to boost start-up firms with a high technological potential. This is the most direct way in which the scientific “community” – universities and public research organisations notably - can transfer its knowledge and competence to industry. They are, therefore, putting in place a range of support or incentive policies (business plan consulting, IP management, funding aids, marketing etc.), to bridge the huge gap separating academia from commercial activities. Along with such institutional arrangements, administrative measures concerning the personnel status of (public-sector) researchers (paid leave to run an incubator, possibility of return to prior position after launching start-up, compatibility of academic status with private ownership etc.) are also being taken. In particular, many authors have for a long time been investigating the two main issues that concern start-up firms, namely intellectual property rights and the search for venture capital. Although these issues are important from the public policy perspective, relatively few studies have been done from the viewpoint of the construction of entrepreneurial competence. After all, it seems very important to extend our knowledge of the links between involvement in the launch of a start-up and academic career paths and to ascertain what significance such an event might have for the career development of scientists and engineers. In other words, we could consider the process of setting up spin-off firms with high technological potential as part of the actors’ professional trajectories and, at the same time, as part of on ongoing process of competence construction. This type of competence analysis combined with studies of professional trajectories could well complement more general analyses of spin-offs. Thus the purpose of this paper is to present, however tentatively, a typological framework that seeks to classify spin-offs in terms of “competence trajectories”. To this end, we draw on the labour market literature on highly skilled scientific and technical experts (academics, scientists and engineers) and combine it with the institutional setting (environment) of start-ups. In this domain, complex interactions between the “scientific community”, innovation policy agencies and firms play a crucial role in shaping different “incentive mechanisms for the creation of spin-offs” and determining the structure of the “intermediate labour market”. It is one of the reasons why we need both to combine labour market analysis with the general dynamics of innovation and to locate it within the overall context of the institutional configuration of R&D.