The Chicago Mixed Board-a-Match teams national bridge championship is held at the summer American Contract Bridge League

American Contract Bridge League

The American Contract Bridge League is the largest contract bridge organization in North America. It promotes the game of bridge in the United States, Mexico, Bermuda, and Canada, and is a member of the World Bridge Federation...

 (ACBL) North American Bridge Championship

North American Bridge Championships

North American Bridge Championships are three annual bridge conventions sponsored by the American Contract Bridge League . The "Spring", "Summer", and "Fall" NABCs are usually scheduled in March, July, and November for about eleven days. They comprise both championship and side contests of...

 (NABC).

The event is a board-a-match team event.
The event typically last 2–3 days with each day being a round consisting of two sessions of 26 boards.
The event is open.
The Chicago Mixed Board-a-Match Teams—one of the oldest ACBL events that was first played in 1929—is a four-session event with two qualifying and two final sessions.