This section is concerned with the format of the national competition only. As is the case with competition rules, the competition format varies greatly among the different regional competitions.
The national competition always consists of two stages: round robin and double elimination.
Round-robin
All competing teams are randomly arranged into several round-robin groups of eight or nine teams each. Every team plays every other team in its group once, receiving 2 points for a win, 1 point for a tie, or 0 points for a loss. The top four teams from each group advance to the single elimination round.
Tie breaks
In the event that two or more teams are tied for one of the top four spots in a round robin group, there are several tie break procedures, applied in the following order:
1. The head-to-head record of all the tied teams is compared. The team(s) with the best record against the other tied teams win(s) the tie break
2. The team(s) with the fewest losses win(s) the tie break
3. The result of the Interactive Science Discovery (ISD) Activity is used. The ISD was a lab-based activity where four team members worked together to solve a challenge in 15 minutes using the materials provided.
In previous years, there was no ISD, so the following procedure was used in its place:
1. If more than two teams are still tied, each team is placed in a separate room and is read ten toss-up questions. Each team's score is determined by the number of questions answered correctly minus the number answered incorrectly. The team(s) with the highest score win(s) the tie break
2. If exactly two teams are still tied, the two teams compete head-to-head, receiving five toss-up questions (no bonus questions are used). All the usual toss-up rules are in effect, including the interrupt penalty. The team with the higher score wins the tie break
If a tie still existed after this procedure, it is reapplied until the tie is resolved.
Single/Double elimination
Approximately 32 teams advance from the round robin (depending on the number of round robin groups). In 2004, exactly 16 teams advanced, while in 2003 and 2002, 18 teams advanced. In 2006, the teams were seeded based on their preliminary round-robin results. In previous years, a team's position in the draw was determined by random draw; teams were not seeded in any way. The competition then proceeds like a typical single-elimination tournament. Unlike in the round robin, a match in double elimination cannot be tied. If a match is tied at the end of regulation, overtime periods of five questions each are played until the tie is broken.
The single elimination system produces a first-place, second-place, third-place and fourth-place team. Prior to the 2006 tournament, a double-elimination tournament format was used. This allowed a fifth place to be added.