Pored over by the media and used as crucial testing grounds for new candidates and campaign techniques by political parties, by-elections – or special elections – are comparatively under-studied in contemporary academic analyses. These elections, held outside the normal election cycle enable local voters to replace a departing representative, but the way in which they vote has often been dismissed as being driven by national factors. In the British case, despite the attention such contests bring, understandings of the way in which people vote in contemporary by-elections are based largely on data from over forty years ago. This article represents a substantial updating of the literature on by-elections, using data on 148 contests from the British context to examine whether pre-existing assumptions from the literature hold: namely the importance of national and local factors. It finds that by-elections no longer represent useful routes by which defeated MPs can re-enter Parliament. For both turnout and party vote share at these contests, a combination of local contextual and national factors impact by-election results, whereas contest specific factors such as having a local candidate only make a difference in a few cases.