The Opening Round game, (formerly known as the Play-In Game) of the NCAA Men's Division I Basketball Championship is the
first game of the tournament, played between the two last-seeded (i.e. 64th and 65th) teams.
The winner of the game is then given a #16 seed and plays one of the #1 seeds that plays on the opening Friday in the first round of the tournament (to give the #16 seed an extra day of rest[citation needed]). To date, no winner of the play-in game has gone on to defeat the #1 seed in the next game. In fact, no #16 seed has beaten a #1 seed at all, including the ones that didn't have to play in the extra game.
The game was first played in 2001, when the Mountain West Conference, which had split from the Western Athletic Conference in 1999, received an automatic bid for the first time. Once the Mountain West Conference received its bid, the number of teams in the field increased from 64 to 65, requiring one team to be eliminated before the tournament entered its traditional 64-team bracket format. The NCAA Women's Division I Basketball Championship accommodated this change by eliminating an at-large bid, decreasing from 34 to 33, rather than adopting the opening round game.
http://en.wikipedia.org/wiki/NCAA_Men's_Division_I_Basketball_Play-In_Game