Exeter Chiefs inflicted Premiship champions Harlequins' second defeat in two weeks with a 42-28 win at Sandy Park.

The Chiefs scored four tries to Quins' three with their fourth coming through Sireli Naqelevuki two minutes from the end to wrap up the result.

Exeter fly-half Gareth Steenson was quick to make an impression on the game with a good break and then the former Ireland Under-21 landed a 25 metre penalty but his opposite number, Nick Evans, saw his attempt to quickly level the scores drift wide of the uprights.

Quins maintained the pressure with Matt Hopper linking-up with his centre partner Jordan Turner-Hall but the England international was stopped short. Chiefs knocked-on but at the scrum the home side were penalised for Evans to get his side back on level terms.

Chiefs crossed for the first try of the game after a break from full back Luke Arscott which, after several phases of play, allowed Phil Dollman to give a long pass to prop Brett Sturgess out on the touchline who ran round behind the posts.

Streenson added the extras and a penalty but Evans kept Quins in touch with his second penalty, from 48 metres as the Chiefs led 13-6 midway through the half. Evans then charged down Steenson's clearance kick to touchdown.

Evans failed with the touchline conversion but following Exeter pressure Steenson landed a second penalty, however England wing Ugo Monye went over for his fourth try of the season with Evans adding the conversion to give the visitors an 18-16 lead at the break.

Exeter made the perfect start to the second half with blindside flanker Ben White going over from close range, as referee Martin Fox continued play after a questionable tackle by Mike Brown on Hopper, and Steenson's conversion took the Chiefs back in front.

Midway through the half, wing Matt Jess saw his pass intercepted by replacement fly-half Rory Clegg who raced up to the Chiefs line, chased by Jess, before passing inside to scrum half Karl Dickson with Clegg converting.

Exeter, sensing a possible upset, responded with two tries in three minutes through inside centre Jason Shoemark to secure a try-scoring bonus point, with Steenson converting the second for a 10-point lead.

The home side were forced to defend their line as the game went in to the final 10 minutes with some strong tackles. But they then gave away a penalty and Clegg landed his second kick to give his side a possible losing bonus point.

But the Chiefs sealed the game with two minutes remaining as replacement Naqelevuki broke clear for Exeter's fifth try and Steenson converted. Munn was yellow carded in the final minute but his side held on for the win.

Exeter head coach Rob Baxter was delighted with his team's performance and hopes they can repeat the showing when they make their Heineken Cup bow next weekend, away to three-time winners, Leinster.

"We will approach Leinster in a similar manner as we did Harlequins,' hesaid. "We are a good side when we play. I want the players to go there and enjoy the experience the full 80 minutes. Now I would like to think that we can really attack the season in the way we did in this game. I don't think many teams will want to stand in front of us if we play like we did against Harlequins."

For Harlequins director of rugby Conor O'Shea the defeat means that his side go into their Heineken Cup match at home to Biarritz on the back of two losses. The Basque club have happy memories of the Twickenham Stoop having won the Amlin Challenge Cup at the venue last season.

"We were rubbish, we were really poor," O'Shea said. "All the credit goes to Exeter for the way they played and we probably should have been beaten by a lot more. It's not terminal, far from it, as we have 20 points after six games. So this will be taken on the chin and the reaction will start next week. I don't care about results, and I said it at half time, I care about performance and today our levels of performance were not right."