A conversational trading system allows a plurality of instruments, for example financial instruments such as foreign exchange products to be traded from a single user interface. The interface includes a deal stack comprising a deal list, a deal detail panel and a button bar. The deal list displays deal related information such as status, party, instrument and an instrument and status related string in a form common to all instruments. The deal detail panel displays information relating to a specific deal in the list that has been selected by the trader in a manner that is specific to the instrument being traded. Deal related information may be entered into the system by trader conversations which are parsed by a parser. The parser analyses the conversation for key terms which depend on the status of the deal. Where a key term is found, the deal status is changed and the deal stack sends appropriate messages to the system which may cause counterparty deal details to change. Deal information may also be entered directly without the use of parsed conversation.