In this chapter we look at communication that takes place between people (peers) with different medical conditions when they join online support groups. Interactions with peers in self-management programmes offer people with different medical conditions the opportunity to share their concerns with similar others, in this way reducing the sense of isolation associated with many illnesses. Such interactions are typically a locus of social support de ned as a ‘transaction of empathy and concern, information and advice, or tangible aid (i.e., goods and services) between two or more individuals’ and characterised by the use of verbal or nonverbal behaviours to seek or provide help (Mickelson, 1997: 157). Such support groups are particularly important for those who suffer from chronic illness as clinical research shows that interpersonal networks signi cantly impact on adaptation to the everyday management of disease. As the concept of supportive community is often deemed central to Internetbased interactions, it is not surprising that participation in online support communities has been hailed as holding a great potential for its therapeutic bene ts. With the likely increase of such communications through dedicated websites and social networking possibilities in the modern era of the Internet, there is a growing need for health professionals and researchers to understand and evaluate such interactions.