Leicester Tigers checked Harlequins' play-off hopes with a thrilling 35-29 win at Welford Road.
Tries from Matt Scott, Ellis Genge and Tom Youngs, between a Nathan Earle reply, put the Tigers 21-5 in front.
Quins replied with a penalty try, but after surviving six minutes with 13 men, the hosts went in 29-12 up at half-time after Genge's second score.
Two Joe Marchant tries and a late Luke Northmore score brought Quins within six points, but the Tigers held on.
Quins stayed fourth after their first defeat in four Premiership matches, but their try and losing bonus points moved them 11 points clear of fifth-placed Northampton, who have a game in hand, while the Tigers ended a three-match losing streak in the league to climb to sixth.
Leicester made a lightning start in a breathless opening, as George Ford's well-timed pass put Matt Scott in before Genge crashed over from close range.
Quins, who had plundered 17 tries in three straight wins, were on the scoreboard within minutes through Earle, but were unsettled by Leicester's ferocity at the breakdown and fell further behind when the returning Tom Youngs benefited from a rolling maul to cross.
The visitors replied once more through a penalty try which earned Dan Cole a yellow card for bringing down the maul, and the Tigers had to play six minutes with 13 men when Genge followed his England colleague to the sinbin for an illegal clear-out.
Yet the out-of-sorts Quins failed to take advantage and Ford kicked a penalty before Genge returned to clinch Leicester's bonus-point try just before the interval.
Ford further extended the lead to 20 points after the break - moving past 1,000 points for the Tigers - and though Marcus Smith's cross-field kick put Joe Marchant in for his fifth try of the season, Leicester looked in full control at 32-19 going into the final 10 minutes.
Yet the Quins, fresh from their last-gasp comeback win over Wasps, launched another fierce fightback as Marchant's great finish and Northmore's 80-metre breakaway try, either side of Zack Henry's penalty, brought the visitors within a converted try of another famous win.
Smith kicked a penalty to touch deep in Leicester's 22, but Steve Borthwick's side withstood the onslaught for their first league victory since 28 March.
Leicester: Steward; Porter, Scott, Kelly, Nadolo; Ford, B Youngs; Genge, T Youngs (capt), Cole, Wells, Green, Martin, Reffell, Wiese.
Replacements: Clare, de Bruin, Heyes, Liebenberg, Brink, Wigglesworth, Henry, Murimurivalu.
Sin-bin: Cole (25), Genge (29)
Harlequins: Green; Marchant, Northmore, Lang, Earle; Smith, Care; Marler, Baldwin, Louw, Symons, Lewies (capt), Lawday, Kenningham, Dombrandt.
Replacements: Gray, Garcia Botta, Collier, Lamb, Chisholm, Landajo, Edwards, Tapuai.
Referee: Luke Pearce (RFU).