Nanotechnology has been established as a priority research and policy focus, cutting across several R&D fields from pharmaceutics, food and electronics. The raise of nanotechnologies has been accompanied by an enduring uncertainty characterising the developments of the scientific knowledge related to this field, as well as the social trajectories of technological applications. Such a condition inevitably affects regulatory responses to such technologies, their development and their uses. This special issue addresses this junction between uncertainty and regulation. With no ambition of (...) providing a comprehensive assessment of such a complex issue, this collection of articles examines three relevant dimensions for understanding uncertainty in nanotechnology regulation, which can be useful entry points for further reflection and discussion: scientific uncertainty, regulatory fragmentation, social actors’ opinions about and attitudes to nanotechnology and regulation. (shrink)