The significantly low rate of HIV infection and high rate of condom use among sex workers in Kolkata, India is partially attributable to a community-led structural intervention called the Sonagachi Project which mobilizes sex workers to engage in HIV education, formation of community-based organizations and advocacy around sex work issues. This research examines how Sonagachi Project participants mobilize collective identity and the manner in which collective identity influences condom use. Using purposive sampling methods, 46 Sonagachi Project participants were selected in 2005 for in-depth qualitative interviews. Taylor and Whittier's (Taylor, V & Whittier, N (1992). Collective identities in social movement communities: lesbian feminist mobilization. In A. Morris & C. Mueller (Eds.) Frontiers in social movement theory. New Haven, CT: Yale University Press) model of identity-formation through boundaries, consciousness and negotiation was used to interpret results. Subjects mobilized collective identity by (1) building boundaries demarcating in-group sex workers from out-group members, (2) raising consciousness about sex work as legitimate labor and the transformative change that results from program participation, and (3) negotiating identity with out-group members. This research establishes a conceptual link between the boundaries, consciousness and negotiation framework of collective identity mobilization and condom use. Condom use among sex workers is motivated by each element of the boundaries, consciousness and negotiation model: condoms mark boundaries, enunciate the consciousness that sex with clients is legitimate labor, and help negotiate the identity of sex workers in interactions with clients.