This paper focuses on some salient issues of urban sustainable development in France with a specific accent on six urban agglomerations: Bordeaux, Lille, Lyon, Montpellier, Nantes and Toulouse. The reticular nature of these issues and the circuits leading to their realization are analysed with reference to the ways a multiplicity of actors conceive, plan and bring about the construction of cities, rather than through sectoral viewpoints. Thus, urban sustainable development appears within a (locally variable) set of linkages that sets these issues firmly in areas of interrelations and intersections. Based on a large body of documentation and field work (observations and interviews) this approach helps trace the complex relations between discourse and the reality of on-going dynamics, including the implementation of sustainable development urban operations such as mutations in the domain of public action as exemplified by urbanisation. These relations converge in articulating the issues, with urban sustainable development – in the diversity of its usages – becoming a “portmanteau”, much like “governance”. In this context, technical experts and the “city professionals” can be seen as intermediary representatives: actors/go-betweens who contribute to the development of links and modes of combining practices between usually separate worlds. On this assumption, we consider that nowadays novel professions directly linked with urban areas and environmental issues are emerging at public local level (cities, metropolitan institutions, town-planning agencies, semi-public companies, associations acting as service providers, etc.), in proportion with the development of an urban sustainable development “repertoire” in urban politics. New specific competences and scopes of activities extend and define the field of sustainable development experts. Nevertheless, these competences remain broken up between several kinds of jobs and functions (civil servants and local government officers, project leaders, urban architects, consultants, employees of associations, etc.). Indeed, the limits of this professionalization process are significant of the success of urban sustainable development itself, which can be interpreted as a malleable concept, a property considered as a central condition of its cognitive and practical diffusion.