[1][2] The show aired as a week-long six-episode tournament at 8:00 p.m. (7:00 p.m. Central) from Monday through Friday with the finale on Sunday.

The second season aired in a weekly format with modified rules from April 4 to July 25, 2008, at 9:00 p.m. (8:00 p.m. Central).

This time, the returning champions format was used and winning contestants compete a series of up to five duels for a $500,000 grand prize.

A partition is raised at the start of each question, after which it is lowered once both players had locked in their answers, allowing the contestants to see each other's choices.

After five nights, the four contestants who won the most duels (and if tied, based on the most accumulated winnings) were invited to the finale to vie for the jackpot.

Her winnings totalled to $1,795,000, including the $75,000 she had earned in previous duels, which made her the highest-winning female American game show contestant to date.

Under the returning champions format, only one contestant, Gabriel Reilich, a former film executive for Reason Pictures / GOOD Magazine, won five consecutive duels for $500,000.

Initial reviews were mixed; some praised the show for bringing something different and original to American television, while others derided Greenberg's hosting on the first night and the amount of "padding" the first episode (which was 90 minutes in length) seemed to have.

Several critics derided the show for giving contestants "stereotypical" titles, such as "The Fire Captain" and "The Alligator Wrestler".

Also since the season premiere, the show was standing and lagging at sixth place behind The CW's second hour of WWE Friday Night SmackDown and the Univision telenovela Pasíon.

Actually ITV in U.K. were the first network to purchase the rights to Duel in September 2007, swiftly followed by ABC in the U.S., who launched their first series of the show, hosted by sport broadcaster Mike Greenberg, on 17 December 2007.

The Duel format was optioned by television networks in Australia, Belgium, Brazil, France, Germany, Hungary, Italy, Mexico, the Netherlands, Poland, Portugal and Spain, but, with the exception of Hungary, Portugal, and Duel's native France, never made it to production in those territories.

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.