First Four

The game was conceived after the Mountain West Conference, which had been formed in 1999 following the split of the Western Athletic Conference, was given an automatic bid for its conference champion, which made it the 31st conference to receive an automatic berth into the men's tournament. Unlike the women's tournament, which accommodated this change by eliminating an at-large bid to keep their field at 64 teams, the organizers of the men's tournament elected to keep their at-large entries at 34. In order to eliminate one of the teams to have a 64-team bracket, it became necessary for another game to be played between the two lowest-ranked teams among the automatic bid leagues.

Florida A&M (2004 and 2007) and Winthrop (2001 and 2010) were the only teams to appear in the game more than once. The 2003 game was the only one to end in overtime.

On April 22, 2010, the NCAA announced that the tournament would expand to 68 teams, with four "Play-In Games" beginning with the 2011 tournament.

In 2011, the broadcast media began calling these games "The First Four" (as opposed to the "Final Four"); and, also used the term "first round games" interchangeably with "opening round games." Formerly, the term "first round game" specifically referred to the first games played by the final 64 teams, not the teams in the opening round. Through the 2015 tournament, these games were known as "second round games," resulting in some confusion for those more accustomed to the round being known as the "first round" and the "second round" being used for the regional quarterfinals (field of 32). Effective with the 2016 tournament, the NCAA reverted to the traditional usage of "First Round" as referring to the first games played by the final 64 teams, and began officially using "First Four" to refer to the opening round games.

The winner of the game was awarded the No. 16 seeded position in one of four regions of the tournament and next played the No. 1 seeded team of that region on the following Friday. Three of the top seeds to beat the opening game winner advanced to the national championship game and all three won the national championship (2002 Maryland, 2005 North Carolina and 2010 Duke). North Carolina was the only No. 1 seeded team matched against the opening round winner more than once (2005 & 2008).

Note that, despite the term "Play-In" game being used colloquially, the loser of the opening round game was still considered to have been in the tournament, as both teams met the qualifications for "automatic tournament entry" as stated in the NCAA Bylaws. At first, only the loser received credit for being in the game for purposes of its conference receiving a share of the NCAA Division I "basketball fund"; however, starting with the 2008 tournament, both teams received credit for playing. There was an actual "play-in" round in 1991, with six teams playing each other (Saint Francis, Pennsylvania versus Fordham; Coastal Carolina versus Jackson State; NE Louisiana versus Florida A&M) before the tournament bracket was announced; these games are not considered part of the 1991 tournament. Consequently, in 2001, Northwestern State technically became the first No. 16 seeded team to win a game in the men's NCAA tournament by virtue of the team's opening round victory.

The teams are not the eight lowest-ranked teams in the field; the four lowest-ranked at-large teams usually have higher rankings among the entire field of 68 than several of the automatic-bid teams coming from the smaller conferences. The four games are held to determine which teams will assume a place in the first round. Unlike other early games in the tournament, the teams are not matched with disparity intended. Rather, equality governs match-ups (e.g., in one game, two teams—usually two of the four lowest-ranked automatic-bid teams—might play for a No. 16 seeding in the first round, while in another game, two teams—usually two of the four lowest-ranked at-large teams—are usually trying to advance as a No. 11 seed).

While most NCAA tournament games are played Thursday through Sunday (with the final game on a Monday), the First Four games are played earlier in the first week, between Selection Sunday and the First Round on Thursday and Friday. As of 2017, two games are played on the Tuesday following Selection Sunday, and the remaining two are played on Wednesday. Once the First Four games are played, the four winning teams assume their places in the bracket of 64 teams, and must play again later that week, with little rest. The two Tuesday winners are paired with their next opponent on Thursday; and, the Wednesday winners play on Friday. With the Second Round being played on Saturday and Sunday, this scheduling allows for six consecutive days of competition during the first week of the tournament.

With the exception of 2019, at least one of the First Four winners has advanced past the First Round of the tournament every year since the format's inception. In 2011, VCU became the first, and to date the only, team to advance from the First Four to the Final Four. In 2020, the NCAA Division I Men's Basketball Tournament was cancelled due to the COVID-19 pandemic.

Unless noted otherwise, the University of Dayton Arena in Dayton, Ohio, has hosted all games. The results of the opening round games since the tournament's expansion to four games are as follows:

^‡The title was later vacated due to NCAA sanctions.