This paper describes cell phone text messaging during the 2004 US Democratic and Republican National Conventions by protesters using TXTmob ? a text-message broadcast system developed by the authors. Drawing upon analysis of TXTmob messages, user interviews, self-reporting, and news media accounts, we describe the ways that activists used text messaging to share information and coordinate actions during decentralized protests. We argue that text messaging supports new forms of distributed participation in mass mobilizations.