The selection committee for the NCAA Bracket 2017 who seeds the whole field of 68 teams from 1-68, but did not make this information public until 2012. The committee then divides the teams amongst the regions. The top four teams will be distributed among the four regions, and each will receive a #1 rank within that region. The next four ranked teams will then be distributed among the four regions, each receiving a #2 rank with their region, and the process continues down the line. Carried to its logical conclusion, this would give each region seventeen teams ranked 1-17, but as seen below, this is complicated somewhat (see the next paragraph and the The First Four section below).
The selection committee is also instructed to place teams so that whenever possible, conference teams cannot meet until the regional finals. Additionally, they are also instructed to avoid any possible rematches of regular season or previous year's tournament games during the Rounds of 32 and 64. Further restrictions are listed in the Venues section below. To comply with these other requirements, the selection committee may move one or several teams up or down one seed from their respective original seed line. Thus, for example, the 40th overall seeded team, originally slated to be a #10 seed within a particular region, may instead be moved up to a #9 seed or moved down to a #11 seed.
The bracket is thus established, and during the semifinals, the champion of the top overall number 1 seed's region will play against the champion of the fourth-ranked number 1 seed's region, and the champion of the second-ranked number 1 seed's region will play against the champion of the third-ranked number 1 seed's region.