As a new, women-led, self-organized and not-for profit amateur sport, women's flat track roller derby initially represented an overt challenge to a broader sports culture. Drawing on in-depth ethnographic research of a UK league, this book presents an analysis of skaters' ambivalent concerns with 'getting taken seriously', traces changes in self-representation and do-it-yourself organization, and develops a sociological account of seriousness in practice. Breeze argues that seriousness is an issue of gender contestation, as skaters are faced with the problem of how to achieve serious recognition. As understandings of roller derby move away from 'a sport for women who don't like sport' towards 'a sport for people who really, really like sport', Seriousness and Women's Roller Derby focuses on moments when skaters' claims for serious recognition simultaneously refuse the terms of such recognition. Skaters move back and forth between practical understandings of seriousness as inevitable, singular and beyond their influence and yet contingent, multiple, ambivalent and created in their own actions. This sociological account of seriousness furthers debate on gender, organization and the mid-ranges of agency between dichotomies of voluntarism and determinism.