In this article we explore the relationship between authentication and identification in the spontaneous hip-hop talk of four young London men from multi-ethnic working-class backgrounds. Whereas sociolinguistic studies of authentication and/or hip hop have frequently focused on the linguistic style of hip hoppers, this article explores hip-hop talk with a specific interest in ‘cultural concepts’ (Silverstein 2004). This focus allows us to discuss how the young men authenticate themselves in relation to a range of other identity performances they discuss, including the ‘white posh girl's’ appropriation of ‘world star’ hip-hop culture or the local South London gang's display of violent gangsta personas. These cultural concepts not only index various aspects of hip-hop culture but also need to be understood in relation to various aspects of larger-scale discourses, practices, and structures. (Hip hop, authentication, indexicalities, cultural concepts)*