Grassroots organizations that have sought to scale up improvements to their urban neighbourhoods through engaging the state have found themselves drawn into relationships with professionals. The potentially negative consequences of such engagements have long been recognized. This paper explores the nature of relations between professionals and organizations of the urban poor, identifying and discussing associated relational tensions. It considers the ways in which one alliance of urban poor federations and support NGOs has responded to the challenge to build alternatives within professionalized mainstream urban development practice.