This study investigates the interactional work involved in ratifying mutual participation in online, multiparty, voice-based chat rooms. The purpose of this article is to provide a preliminary sketch of how talk and participation is managed in a spoken communication environment that comprises interactants who are not physically copresent but are engaging in and disengaging from conversations with high regularity. This distinctive feature of chat rooms provides a unique opportunity to examine how communication is shaped by technological affordances and constraints, an issue important to a number of different areas of study, including discourse analysis and computer-mediated communication. The analysis examines two aspects of interaction that are germane to participating in chat rooms: summons-answer exchanges and verbal alignment. The findings show that talk in chat rooms does not simply happen but is preceded by highly organized, complex, and collaborative interactional work aimed at establishing mutual orientation. (Contains 1 figure and 2 footnotes.)