The formation of group norms in computer-mediated communication (CMC) was examined among students who used e-mail as part of a course. A network analysis of group structures revealed that (a) content and form of communication is normative, group norms defining communication patterns within groups, (b) conformity to group norms increases over time, communication outside the group is governed by different social norms. Results show that norms prescribing a particular use of technology are socially constructed over time at the level of locally defined groups and also show that the influence of these norms is limited to the boundaries of the group. It is concluded that the process of social construction is restrained by social identities that become salient over the course of interaction via CMC. These findings complement experimental evidence that stresses the importance of normative influence in CMC.