Systems and methods are disclosed for tracking and displaying the logon status of selected co-users of an on-line or network system in real time to a tracking user in a unique graphical interface. The invention provides user definable on-line co-user lists, or “buddy lists,” which track specific co-users in real-time automatically. When a user logs on to a system, one or more of the user's buddy lists are presented to the buddy list system. The buddy list system attempts to match co-users currently logged into the system with the entries on the user's buddy list. Any matches are displayed to the user. As co-users logon and logoff, a user's buddy list is updated to reflect these changes. An indication can also be added to show that a co-user just logged on or just left the system.