This dissertation focuses on social interaction patterns between young people in an online chat room, analyzing how social order is displayed and constituted. An overall issue concerns when and how the participants manage to co-create social communities within this setting. The data draw on an ethnographic study, where chat room observations and online recordings were carried out during three years. Methodological guidelines from discursive psychology and conversation analysis have been used in making detailed sequential analyses of chat room interactions. The thesis builds on social practice theories, including sociocultural theorizing and studies of language socialization, and work on positionings. The findings show that familiarity with chat language, including the use of emoticons and leet speak, as well as familiarity with netiquette and conversational routines such as greeting- and parting routines, are vital for the participants in order to become parts of local groups and alignments. Playful improvisation is an important feature in the chat room intercourse. Moreover, full participation requires involvement in the lives of co-participants and extended dialogues over time. In the process of moving from peripheral to more central participation, the participants formed alignments with other participants and positioned themselves and their co-participants in the chat room. Such alignments were often founded on a shared taste in, for example musical genres and everyday consumption patterns. Shared views on school, sex and relationships, as well as age or gender alignments also played a role in the creation of local communities. Conversely, issues of exclusion were recurrent features of chat room interplay. All considered this created participation patterns that formed local hierarchies which were not fixed or static, but rather fleeting and dynamic. And yet, the participants generally did not transcend or challenge contemporary age and gender boundaries.