The precipitous decline in union density and influence around the world has spawned a growing body of scholarship on union renewal. While this literature evidences lively debates regarding the efficacy of different renewal strategies, many argue that the path to renewal is paved through increased member activism. In this article, we question that premise. We examine the importance of rank-and-file union member activism in 44 cases of organizing campaigns in the United States and in the UK. Our review of these cases reveals little support for the notion that member activism is indispensable to union renewal in general, and successful organizing campaigns in particular. Our findings provide additional insight into the debate over top-down and bottom-up strategies for renewal, and raise several questions for future research regarding when, under what conditions, and under what rules worker activism matters for labour union renewal. Copyright (c) Blackwell Publishing Ltd/London School of Economics 2009.