Embodiments of the present disclosure target advertising to a group of related users of a social networking system. To target advertising to a group of users, the social networking system receives targeting criteria specifying a group to receive an advertisement at substantially the same time. To identify a group of users of the social networking system satisfying the targeting criteria, the social networking system observes the interactions of connected social networking system users. Connected users interacting with each other in a manner that satisfies the targeting criteria may be added to a group. The social networking system serves the advertisement to a set of users included in the group because the served users are members of the group.