We examine an important recent organizing success of the US labour movement: the ‘Justice for Janitors’ campaign in Los Angeles. This campaign has spanned a complete business cycle and shows the union’s capacity for growth over time. It illustrates the potential for unions to overcome pro–employer bias of labour laws, as well as their efficacy in appealing to the wider public. It exposes the importance of building coalitions, as well as the value of union analysis of legal, industrial, and political conditions. Our analysis suggests conditions under which unions might survive and thrive in the service sector in the twenty–first century.