This paper begins in Section 1 by noting two processes that have been generally overlooked in sociolinguistics. Firstly, the prevailing approaches to ethnicity have tended to neglect the processes through which individuals can either adopt someone else's ethnicity, or get together with them and create a new one. Secondly, socialization in sociolinguistics is most commonly seen as enculturation into an ingroup, not as a process of learning to like and live with social and ethnic difference. To throw some light on these two processes, the paper turns its focus towards a practice it calls 'language crossing' ('code crossing', 'crossing'). Language crossing involves code alternation by people who are not accepted members of the group associated with the second language that they are using (code switching into varieties that are not generally thought to belong to them). This kind of switching involves a distinct sense of movement across social or ethnic boundaries and it raises issues of legitimacy which, in one way or another, participants need to negotiate in the course of their encounter. A fuller account of the intricate dialectic between language, peer group belonging and ethnic otherness that lies at the heart of language crossing emerges as the paper proceeds. After some methodological preliminaries (Section 2) and an outline of some of the ways in which the multiracial peer group I studied can be considered a community (Section 3), the empirical description of crossing itself begins with an initial emphasis on the way that crossing was integrated with what was shared in peer group culture (Section 4). The following section (Section 5) turns to the way in which crossing processed ethnic division and race stratification within the peer group, and this is further elaborated in the discussion of socialisation in Section 6. Section 7 contains a conclusion which briefly links crossing's treatment of ethnicity with Bourdieu's discussion of doxa, orthodoxv and heretical discourse.