In our case study, we examined the instant messaging (IM) workplace discourse of a pair of expert IM users. We found that the participants maintained discourse cohesion and thus coherence via short, rapidly sent transmissions that created uninterrupted transmission sequences. Such uninterrupted transmission sequences allowed each participant to maintain the floor. Also, the participants used topicalizations and performative verbs to maintain coherence. We also found that the participants' use of short transmissions may have ambiguated their enactment of their institutional roles and the rights afforded to them by those roles.