Harlequins stretched their Aviva Premiership record for the season to 10 wins from 10 matches when they beat London Wasps 16-22 at Adams Park.
The result means Quins have now won 14 consecutive games in all competitions and lead the Premiership standings by nine points.
Tries from Matt Hopper, Mike Brown and Luke Wallace gave Harlequins a hard-fought victory over a determined home outfit.
Harlequins had a try ruled out in the opening stages of the match when Mike Brown was held just short of the line after he had snapped up Nick Evans' cross-field kick. But the visitors were on the score sheet minutes later when Joe Marler fed the ball to Matt Hopper who crossed for a try, converted by Evans.
Wasps struck back quickly with a penalty from Nick Robinson after intense home pressure on the league leaders' line.
Quins absorbed more pressure for the remainder of the half but were finally breached on the stroke of half-time when Robinson struck with the boot to reduce the vistors' advantage to a single point.
Following the restart it was Evans who kicked Harlequins back into a four-point lead following an infringement at the scrum.
6-10 then became 6-15 when Mike Brown crossed for a try after a sublime bit of handling from Quins after they had stolen the ball at the line-out. The conversion was missed.
The visitors then established what would turn out to be an unassailable lead when Luke Wallace collected Danny Care's superbly weighted chip to score. Evans added the conversion and Wasps needed to find 16 points in the final quarter to avoid defeat.
The comeback began on 64 minutes when Hugo Southwell charged over out wide. The conversion was missed but a stunning score from Tom Varndell with ten minutes remaining gave Wasps real hope.
There was to be no crucial third try from the gutsy hosts though, as Quins held on for yet another important win.
London Wasps (6) 16 Harlequins (7) 22
Scorers
London Wasps
Tries: Southwell, Varndell
Pens: Robinson 2
Harlequins
Tries: Hooper, Brown, Wallace
Pens: Evans
Cons: Evans 2
Referee: Dean Richards (51st Premiership game)
Teams
London Wasps
15 Hugo Southwell , 14 Tom Varndell , 13 Dominic Waldouck , 12 Riki Flutey , 11 Christian Wade , 10 Nick Robinson , 9 Joe Simpson , 8 John Hart (c), 7 Matt Everard ,6 Richard Birkett , 5 Marco Wentzel ,, 4 Ed O'Donoghue , 3 Ben Broster , 2 Rob Webber ,1 Tim Payne
Replacements :16 Tom Lindsay , 17 Zak Taulafo , 18 Jeremy Castex , 19 Joe Burton , 20 Sam Jones , 21 Charlie Davies , 22 Ryan Davis , 23 Elliot Daly
Harlequins
15. Mike Brown , 14. Seb Stegmann , 13. Matt Hopper , 12. Tom Casson , 11. Sam Smith , 10. Nick Evans , 9. Danny Care, 8. Chris Robshaw (C), 7. Luke Wallace , 6. Maurie Fa'asavalu , 5. Charlie Matthews , 4. Tomas Vallejos , 3. James Johnston , 2. Joe Gray1. Joe Marler
Replacements:16. Chris Brooker , 17. Mark Lambert , 18. Kyle Sinckler , 19. Pete Browne , 20. Will Skinner , 21. Richard Bolt , 22. Ben Urdapilleta , 23. Ugo Monye
