Season 1

Each player began a duel with ten chips, each worth $5,000 (for a combined total of $50,000). Before each question was asked, a screen rose between the contestants to hide their answers from each other. The duel always began with the catchphrase "Let's Duel!" before the question was heard. Each question was multiple choice with four choices. The question was read by the host while the contestants used their chips to cover choices, one chip per choice. They were allowed to cover any number of choices, provided they had enough chips. After both players had locked in their answers, the screen was lowered so contestants could see each other's choices, and the correct answer was then revealed. All chips placed on wrong answers were taken away, and their value was added to a jackpot.

While the questions normally had no time limit, a contestant who had already locked in his/her answers could "press" the opponent and impose a seven-second time limit, after which answers would be automatically locked in. Each contestant was given two presses per duel.

The duel continued until at least one contestant failed to cover the correct answer to a question. If only one contestant failed to answer correctly, that contestant was eliminated; any chips the contestant had not played were not added to the jackpot, though any played on wrong answers were still added. The winning contestant became champion and won the value of any chips they still possessed, including the one covering the correct answer. That money was theirs to keep, regardless of the outcome of future duels.

If neither player covered the correct answer, however, the duel went to a sudden death "shootout". For the shootout, there were no presses and each player received four new chips with no cash value. If only one player answered correctly, that player won the duel and became champion, but won no money. If both players answered correctly, the player who covered fewer choices won. (It is unknown what would have happened in any other situation, as no such situation ever aired.)

The champion then chose a new challenger from a randomly selected group of three from the remaining members of the "Players Gallery" (those in the contestant pool who had not yet participated), based on a small amount of information revealed about each potential contestant. Contestants who had dueled were ranked by number of duels won, and then by cash winnings as a tiebreaker; After five nights, the four top contestants competed for the jackpot on the finale.^[5]

During the finale, the top-seeded player was given the choice of which other finalist he wanted to face in the first semifinal duel, leaving the two other finalists to play in the second. The winners of each semifinal advanced to the final duel to play for the entire jackpot. The final round duel played the same as the qualifying duels, with lost chips continuing to add to the jackpot, and any winnings kept. The winner of the final duel claimed the jackpot, as well as all earnings accumulated in previous duels.

Season 2

The way questions were played remained the same, but the producers changed the game format to accommodate continuing weekly episodes. First, each contestant received one press per game rather than two. Second, the chips had no monetary value; instead, the prize value of a duel was determined by its length. Thus, unlike the first season's tournament, the potential prize increased as a duel progressed:

If both contestants missed a question, the value of the duel was frozen at the previous value; the format of the "shootout" used to determine the winner was identical to the tournament format.

For the weekly series, a bonus round was added after each duel. The winner was asked a single "Max Question" and was given one chip and seven seconds to respond. A correct answer doubled the contestant's winnings from the just-played duel, for a potential maximum of $100,000. There was no penalty for a wrong answer.

Winning contestants then had the option to take their winnings and leave, or to risk them to play another duel against their choice of three contestants. If they lost in their second or third duel, they forfeited all their winnings, while a loss in their fourth or fifth duel cut their winnings in half. A contestant who won five duels in a row had his/her winnings increased to a total of $500,000, without having to play a Max Question after the fifth victory, and retired as an undefeated champion. When a contestant chose to leave or won the jackpot, the next two contestants to play were the ones not chosen by the champion for the previous duel.

Nielsen ratings

Hungarian version

The game is produced in Hungary titled Párbaj (Hungarian for Duel), starting on 31 August 2009 on TV2. It is hosted by István Vágó. It runs on weekdays from 19:05 to 20:15.^[10] After each duel, the winner it is given a bonus question with 3 tokens to use. Winnings are determined by the number of duels won and the number of tokens used in the bonus question (as long as the correct answer is chosen). The highest prize is possible after winning 5 duels and its value is 25 million forints. Players have 2 accelerators per duel. The phrase at the beginning of each duel is "En garde!".

A web version of the game is available on TV2's official website.

French version

France 2 was the third network to obtain the rights to the game show under the name Le 4e duel, aired on 2008 until 2013.