Abstract: The invention concerns trading tokens, such as but not limited to, the trading of virtual trading cards. The invention also concerns a computer system (104) to facilitate the trading of tokens, a set of messages exchanged in order to trade tokens, a method of trading tokens by a token owner, and a software application to be used by the token owner to trade a token. Information relating to tokens owned by the first and second user is stored in a datastore. Using their mobile device (100), a first user (102) offers to trade a first token, and this offer is stored in the datastore (104). The server (104) then sends to the mobile communication device (112) of a second user (110) details of the offer. The second user (110) can reply by offering a second token in exchange for the first token, and this offer is also stored in the datastore and communicated to the first user (102).