This paper takes as its platform a body of work which often draws upon - or rather, is located at the intersection of - philosophy, feminist theory and science studies and which frequently deploys concepts such as materiality, ontology, process, and performativity in order to offer non-reductionist accounts of the material world. It seeks to shift the focus of attention in this work slightly in order to ask not how something comes to matter, or what it is that materialises, but rather: what matters? It begins by briefly exploring the ways in which three different theoretical interventions, interventions which might loosely be described as 'post-constructivist', seem somehow to lose slight of the very thing that is at the heart of their analyses (the very things that matter to them). These are: events, in Deleuze's account of the difference between a fact and an event in The Fold (2001); values, in Latour's account of a fact and a value in Politics of Nature (2004b); and (political) difference/transformation in Law and Urry's account of the constitutive power of social science research methods in 'Enacting the Social' (2004). The paper goes on to argue that the concept of event holds some potentially useful orientations with regards the question 'what matters?' and also, importantly, that insofar as this concept overlaps with theories of materialisation, it neither compromises nor betrays the valuable contributions of work in this area.