The present invention provides presence information to a subscriber indicative of the availability of a user who is already actively participating in a communication session. A presence system receives and processes participation information, which bears on the degree in which the user is participating in the communication session, and generates the presence information based on defined processing rules. The resultant presence information may indicate whether the user can be interrupted to accept other communications while engaged in the communication session. If the user can be interrupted, the presence information may also identify the most appropriate methods to contact the user during the communication session.