Mirco Antenucci scored twice as Leeds recorded an impressive 2-0 win over Championship leaders Derby at Elland Road.
United clinched their first win against the Rams since September 2005, some 12 games ago in their rivalry. That Derby won 10 of that dozen made it an all the more frustrating record for the Whites.
Another poor run of one win in their last 10 games hardly inspired confidence either, but Antenucci's double powered Leeds on as Steve McClaren's men were rattled in a way they rarely have been this season.
Derby looked the better bet in the opening quarter but once Leeds started to dominate in midfield, the home side took control.
That had not appeared likely early on as McClaren's men - with six wins in seven on the road - settled the quicker of the sides.
For all that, though, their best early offerings were a wide attempt from Jeff Hendrick and a couple of half-openings for Chris Martin in the wake of defensive lapses.
Giuseppe Bellusci also had to be pinpoint with a last-ditch tackle on a clean-through Jonny Russell, before the hosts started to impose themselves.
In a fiery opening 30 minutes they had three men booked but once they started tackling cleanly and keeping the ball, they looked markedly better.
It was soon Derby's players swinging and missing, two of their men having their names taken, with Omar Mascarell one of those booked as he tried in vain to take down Alex Mowatt, who forced Lee Grant into a smart save.
With Mowatt and Lewis Cook first to the ball, more Leeds chances came and 43 minutes in they scored. Will Hughes lost out to Mowatt, his ball found Souleymane Doukara and his pass from the left of the box was tucked in by Antenucci.
The same man was on the spot six minutes after the break too to add a second. Captain Stephen Warnock got down the left, pulled the ball back and Antenucci showed terrific composure to beat Grant.
Sam Byram went in pursuit of a third and was denied by Grant after a mazy run on the right, while Derby felt they had a penalty shout on the hour mark. Liam Cooper - already booked - brought down Cyrus Christie on the very edge of the box. Referee Mick Russell validated the decision with his assistant, stuck to his original call and the free-kick was cleared as Derby protested.
McClaren made a triple change to try to pep up his men but Leeds continued to press, Antenucci being denied a hat-trick as Grant got down well to shove away a low drive.
Derby should have made a fist of it with 10 minutes to go, Kwame Thomas wildly off target from 10 yards after a brilliant Warnock clearance off the line, and with that their chances went.