Using iCal 2.0 or later, you no longer need to change the status of an event as attendees respond to your event invitations.

Instead, the people you invite to the event can choose their attendee status, and that status is reflected in your event (by the icons that appear next to attendee names in the Info drawer or in the event's title bar) when you receive their responses.

For more information about inviting people to events, responding to event invitations, or the symbols that appear next to events or attendees, click "Tell me more."