© Urban Studies Journal Limited 2016. For some time now, the field of urban studies has been attempting to figure the urban whilst cognisant of the fact that the city exists as a highly problematic category of analysis. In this virtual special issue, we draw together some examples of what we call urban concepts under stress; concepts which appear to be reaching the limits of their capacity to render knowable a world characterised by the death of the city and the ascent of multi-scalar de-territorialisations and re-territorialisations. We organise the papers selected for inclusion into three bundles dealing respectively with complex urban systems, the hinterland problematic and governing cities in the age of flows. The phenomenon of urban concepts under stress stems from the existence of a gap between existing cartographies, visualisations and lexicons of the urban and 21st century spatial conditions and territorialities. Given that this disarticulation will surely increase as this century unfolds, a pressing question presents itself: what is to be done with the field of urban studies after the age of the city? In this introduction, we argue that there exist at least six ways of responding to the present conceptual difficulties, each implying a different future for urban studies. We place under particular scrutiny voices which argue that nothing less than a scholarly tabula rasa will suffice. Our conclusion is that the phenomenon of concepts under stress provides an opportunity to think afresh about what to do with the field of urban studies and that it is premature to foreclose discussion about possible futures at this point.