Introduction: Much debate about scientific realism concerns the issue of whether it is compatible with theory change over time. Certain forms of ‘selective realism’ have been suggested with this in mind. Here I consider a closely related challenge for realism: that of articulating how a theory should be interpreted at any given time. In a crucial respect the challenges posed by diachronic and synchronic interpretation are the same; in both cases, realists face an apparent dilemma. The thinner their interpretations, the easier realism is to defend, but at the cost of more substantial commitment. The more substantial their interpretations, the more difficult they are to defend. I consider this worry in the context of the Standard Model of particle physics.