1. A conversational dealing system for trading instruments between counterparties, comprising a plurality of trader terminals each having a user interface for inputting and displaying to the trader deal related information, the trader terminals communicating with each other via a communications network, wherein the trader terminals user interfaces further comprise: a deal stack holding a plurality of deals in which the trader is participating, the deal stack including the status of each deal and a deal description; and means for entering conversational deal related information; and the trader terminals further comprise: a parser for parsing the conversational deal related information to detect a change in or an intention to change deal status; and for notifying the deal stack of the change in deal status; whereby on receipt of a changed deal status notification, the deal stack generates deal string appropriate to the new deal status.