This paper consists of a discourse analysis of data collected from websites that have been created by and for people who wish to share experiences of eating disorders in a positive and supportive environment. These sites have earned the broad description `pro-ana' (where `ana' is short for `anorexia'). Site users have come to see themselves as a broad on-line community of like-minded individuals, but within this community there are many subgroups, and the boundaries between these subgroups are fiercely contested. In addition, frequent attacks on such websites in the media (charged with `promoting eating disorders'), and by occasional hostile site visitors, have often forced the community into a defensive mode. The result is a rich tapestry of identity work. The analysis examines several `pro-ana' sites and explores the way in which the identity is used to police the boundaries of the community, and ultimately, what it means `to be ana' rather than `mia' (bulimic), `a normal', `a faker', or even `a hater'.