Martyn Woolford and Scott Malone's second-half efforts were enough to give Millwall a 2-0 victory over bitter rivals Leeds United at the New Den.
Woolford struck after 65 minutes and Malone 11 minutes later to give the Lions their third successive Championship victory and condemn Leeds to their third league loss in as many games.
In a typically feisty atmosphere, Rodolph Austin broke forward from midfield in the second minute and fired a long-range effort that went just wide of David Forde's goal.
After that the first 15 minutes were scrappy and tight, both sides exchanging possession but not creating any real clear-cut chances.
That was until Stephen Warnock was shown an 18th minute yellow card for a cynical foul on Woolford as the Lions broke forward.
On 25 minutes, Alex Mowatt received Michael Tonge's chipped through-ball as he darted into the area and attempted a hooked shot but his effort was collected by Forde.
Millwall's first real chance saw Martyn Waghorn hit the post with a 29th-minute shot after darting into the box and Woolford rifled the rebound high and wide.
Three minutes later, Waghorn's left-wing corner found Danny Shittu who headed his effort wide of Paddy Kenny's goal.
Luke Murphy, a summer signing from Crewe, replied for the Whites with a driven long-range effort in the 37th minute but his shot rose comfortably over the bar.
Another ex-Crewe man, Luke Varney then attempted an ambitious overhead kick a few minutes later but his effort was also off-target.
Millwall had a penalty appeal turned down just before the break by Chris Foy after Malone darted into the box and was adjudged to have been tackled cleanly by Austin.
In first-half stoppage-time, Jason Pearce found himself under pressure in the Millwall box and launched a close-range effort into the stands.
After the break, Liam Trotter tried his luck from range like many others did but his shot was as wayward as several before him.
Ross McCormack should have given Leeds a 48th-minute lead but he failed to connect properly with Mowatt's teasing left-wing cross.
The Lions opened the scoring just after the hour when Woolford received the ball on the edge of the area and guided his shot past a diving Kenny.
As Leeds searched for an equaliser, Brian McDermott threw on Sam Byram and Matt Smith as the Yorkshire club went more attacking.
But Malone put the tie to bed with a cool 76th-minute strike after exchanging passes well with Liam Trotter.
The home side nearly had a third three minutes later when Waghorn forced a good save from Kenny and the rebound was just missed by Woolford.
And with the resulting punt up field, Malone deflected the ball past his goalkeeper and rushed back to make amends with a goal-line clearance.
Millwall again nearly added a third through Woolford with four minutes left after his chip over an onrushing Kenny hit the post.
But Steve Lomas' men ran the clock down to register their 600th victory in second-tier football.