London - Kemar Roofe gave Leeds a 1-0 win at Derby in the first leg of a feisty Championship play-off semi-final that saw the hosts angered after a controversial penalty reversal.
Roofe slotted home early in the second half for his fourth goal against Derby this season to reward a dominant display from Marcelo Bielsa's side.
But Leeds were left breathing a huge sigh of relief when referee Craig Pawson overturned his decision to give Frank Lampard's men a penalty with 12 minutes to go after Jayden Bogle and Jack Harrison collided in the box.
Derby's furious protests were in vain and they now need a second leg comeback at Elland Road on Wednesday, with no side ever reaching the Championship play-off final having lost at home in the first leg.
It was the latest controversy involving Leeds and Derby this season.
Leeds' win over Derby in January was overshadowed by the 'spygate' affair after Bielsa's admission that he had sent a member of his staff to "spy" on the Rams training the day before the game.
Bielsa later admitted that he had sent staff to watch "the training sessions of all opponents", with Leeds fined £200,000 by the Football League for their part in the incident.
Leeds are looking to return to the Premier League for the first time in 15 years and they are on course for a Wembley final against Aston Villa or West Bromwich Albion on May 27.
Villa lead 2-1 after their first leg earlier on Saturday.
Derby, who have been promoted just once in eight play-off attempts, started brightest, with Tom Lawrence curling a sixth-minute effort wide.
But Leeds grew into the game and Roofe sent an overhead kick wide in the 19th minute, before Luke Ayling failed to make the most of a back-post header three minutes later.
Stuart Dallas volleyed narrowly wide in first-half stoppage time as the visitors ended the half strongly.
And the pressure finally told in the 55th minute when Roofe met Harrison's superb low cross with a cool finish.
Kelle Roos pulled off a superb full-stretch save to deny Roofe a second a minute later as Derby were left rocking.
It should have been 2-0 when Pablo Hernandez missed the ball with the goal at his mercy in the 63rd minute.
Pride Park erupted when Derby had their penalty withdrawn after the referee initially ruled Harrison had fouled Bogle, a decision made following consultation with assistant referee Eddie Smart.