Robert Snodgrass ensured Leeds gained revenge over Watford to book his side's place in the third round of the Carling Cup with an extra-time winner.
The last time the two sides met Watford ran out comfortable 3-0 winners in the 2006 Championship play-off final with Leeds then suffering relegation to League One the following season.
But they continued their 100% start to the campaign thanks to a Snodgrass brace, the second of which came after substitute Marvin Sordell had produced an 87th-minute equaliser for Watford, who last won at Elland Road in 1988.
Watford, who revealed before the game they have accepted an offer from Portsmouth for striker Tommy Smith, made a bright start and Will Hoskins - looking for his first goal since January - saw his header fly wide from close range.
Leeds responded and Bradley Johnson's drive from the edge of the box cleared the frame of the goal.
But home goalkeeper Shane Higgs - with three clean sheets this season - kept his side on level terms in the 19th minute, producing a brilliant save to tip Don Cowie's 25-yard drive away for a corner.
Good work from Mike Grella then created an opening for Snodgrass but after his first shot was blocked by Lloyd Doyley, the Leeds forward could not keep his next effort down.
Danny Graham then saw his drive saved by Higgs before Tom Cleverley's weak shot fell harmlessly wide.
But Leeds moved in front in the 38th minute when Snodgrass curled his shot into the bottom corner from 12 yards.
The Hornets responded and came close to equalising within four minutes but Higgs was on hand to keep out Graham's effort.
Just before the break, Jermaine Beckford, with four goals in as many games, saw his goalbound effort blocked by Mike Williamson before Leeds survived another scare.
First Higgs did well to push Cleverley's deflected effort around the post and from the resulting corner, Graham couldn't direct his header on target.
Beckford tried his luck from 35 yards, his strike failing to trouble Richard Lee, before Jonathan Howson struck a drive from 25 yards wide.
The Hornets came agonisingly close to restoring parity when Cleverley's drilled shot from 20 yards beat Higgs but it came back off a post.
Leeds nearly took advantage of their let-off when Snodgrass unleashed another effort which forced Lee into a fine save.
Beckford thought he was going to extend Leeds' lead 20 minutes from time but Lee pulled off an excellent save to deny the striker.
Sordell forced extra time when he fired home with three minutes left but Snodgrass pounced following a flick on by Enoch Showunmi in the 98th minute to book Leeds' place in the third round.