10 yards.
Another answer:Theoretically, the "longest down" could be almost the entire length of the field, thanks to yards lost due to fumbles, sacks or penalties. One of the playoff teams in Wild Card Weekend 2012 (I forget which one) faced a 4th down with 29 yards to go. They punted, as you might expect.Lions
2 & 65
Detroit lions 2nd 65 yards
morten Anderson nfl from 86 to 08
17
Me
Longest GainIt's the longest reception caught in the game.
The longest down in NFL history was in the game between the Detroit Lions and the Chicago Bears on Sept. 17, 2006. After jumping offsides 3 plays in a row, the lions were then penalized 4 times consecutively for holding resulting in an amazing 2nd down and 65. They were unable to convert. ======================= This is inaccurate. First, it's impossible for the offense to commit an offsides penalty. They would have to false start to do so, at which point the play is dead. Second, the longest down and distance in that game, according to NFL.com, was 2nd and 31. Answers.com won't allow me to link the source, but go to gamecenter on NFL's site and look up that game.
The longest play you can make in the NFL is for a receiver in the end zone to run a kickoff back for a touchdown. A lot of players have done it.
michael viks longest run is 53 yards.
FAVRE
Lamar hunt