Exeter Chiefs and Harlequins were separated by a single point in a 26-25 win for the home side at Sandy Park.
The first half was fiercely contested, a penalty try and tries from Nick Evans and Charlie Walker helped Quins establish an early lead.
However, the boot of Gareth Steenson kept the Chiefs within touching distance with four penalties.
A magnificent try from James Short put Exeter into a half-time lead. Quins fought back but profligacy from the tee meant that they were never able to full extend any advantage they could forge.
Steenson, on the other hand, was in electric form and topped off his kicking performance with what proved to be the winning try.
Tim Visser scored a try in the 62nd minute for Quins, securing bonus point but the conversion was missed and this was as it stayed.
A 77th-minute penalty for the vistors was missed and the Chiefs held out for an excellent victory.
The Chiefs went ahead in the first minute through a penalty from Gareth Steenson. This lead was short-lived as Quins responded with a penalty try in the seventh minute.
Referee Matt Carley deeming that the Exeter defence had illegally held up the visitors' pack as they attempted to push over from a scrum.
Steenson added a second penalty in the tenth minute before Harlequins scored their second try of the match, Evans crossing in the corner before missing the conversion taking the score to 6-12.
Exeter's Steenson made it three from three with a penalty in the 24th minute. Five minutes later Quins scored their third try of the match with Walker going over in the corner to extend his side's lead to eight points after Evans missed a tough conversion.
Once more Steenson kept his side in touch of their opposition with a fourth successful penalty kick in the 32nd minute to cut the defecit to five points.
This gap was bridged with a try from Short, a mistake made by Harlequins and quick ball across the backs found the wing who crossed in the corner. Steenson made no mistake with the conversion to put the Chiefs into a 19-17 lead at the break.
In the 42nd minute Evans fired the visitors into the lead with a penalty. The hosts got themselves back into the lead as Steenson added a try to his tally of four penalties in the 55th minute.
The fly-half converted to give his side a six point lead. Elvis Tainone was sent to the sin-bin for Exeter in the 61st minute for a dangerous tackle.
The visitors capitalised on this a minute later with a bizarre try. The ball bounced off the corner flag into the hands of Visser who went over in the corner.
Tim Swiel missed the conversion to make the score 26-25. Swiel missed another kick in the 77th minute which would have given Quins the lead, the ball drifting wide in strong winds. This proved to be Quins' last chance as it finished 26-25.
Tries: Short, Steenson
Cons: Steenson 2
Pens: Steenson 4
Yellow Cards: Taione, Johnson
Tries: Penalty Try, Evans, Walker, Visser
Replacements: 16 Elvis Taione, 17 Ben Moon, 18 Alex Brown, 19 Geoff Parling, 20 Tom Johnson, 21 Dave Lewis, 22 Sam Hill, 23 Olly Woodburn
Harlequins: 15 Mike Brown, 14 Charlie Walker, 13 George Lowe, 12 Harry Sloan, 11 Tim Visser, 10 Nick Evans, 9 Danny Care (c), 8 Nick Easter, 7 Dave Ward, 6 Chris Robshaw, 5 Sam Twomey, 4 James Horwill, 3 Kyle Sinckler, 2 Rob Buchanan, 1 Joe Marler
Replacements: 16 Joe Gray, 17 Mark Lambert, 18 Will Collier, 19 Charlie Matthews, 20 Kieran Treadwell, 21 Tito Tebaldi, 22 Tim Swiel, 23 Matt Hopper
Referee: Matthew Carley
Assistant Referees: Ros Campbell & Roger Baileff
TMO: Keith Lewis