Click on Below result for game report.
Leinster extended their unbeaten run in the Heineken Cup to seven games to book a semi-final clash against another French side at Lansdowne Road.
There was a tournament-record crowd for a Cup quarter-final of 45,000 at the home of Irish rugby today to see Brian O'Driscoll's side book a ticket to meet Perpignan on the weekend of April 25-26.
It took 29 minutes for Leinster to turn their territorial superiority into points when Brian O'Meara kicked a simple penalty goal.
Seven minutes later, backrower Keith Gleeson ran in from 25 metres for an overlap try which O'Meara converted.
An O'Meara penalty goal on the stroke of halftime gave the Irishmen a 13-0 lead at the interval after playing with the stiff breeze.
French champions Biarritz notched their first points a minute after the break when international scrum-half Dimitri Yachvili kicked a penalty goal, but Leinster hit back almost immediately with a power try from No 8 Victor Costello as he converted a driving maul from 15m out into a try.
Denis Hickie was denied a try by the video referee when he was adjudged to have lost the ball on the line and midway through the half, Yachvili added a second goal from 40m.
Biarritz applied more and more pressure as the game wore on and forced Leinster to show off their defensive capabilities.
Then there was drama in the 10 minutes of injury time allowed by English referee Steve Lander as Biarritz No 8 Thomas Lievremont peeled around the front of a close-range lineout to claim his side's first try.
Yachvili's touchline conversion cut the gap to one score and if centre Marc Stcherbina not been caught from behind as he chased a kick through, Biarritz could have won in the 95th minute of the match.
Leinster: Tries - K Gleeson, V Costello; Pens - B O'Meara 2; Con - B O'Meara.
Biarritz: Try - T Lievremont; Pens - D Yachvili 2; Con - D Yachvili.
Heineken man-of-the-match: Eric Miller (Leinster)
Heineken Cup specialists Toulouse cruised into the final four with an impressive 16-point victory over Northampton, in front of 36,500 fans at Stade Toulousain.
Wayne Smith's Saints never really found their rhythm, and the French giants hassled and harried their way to a 19-6 lead at the break before powering into the semi-finals with a determined second-half show.
The first half was shaping up to be a kicking dual between Saints man Paul Grayson and Toulouse s young gun Yann Delaigue with Delaigue slotting three and Grayson two after 25 minutes.
Delaigue turned down a chance at goal in the 35th minute, but scrum-half Frederic Michalak stepped up and slotted it.
But the fans were to see a try in the first half, in the 39th minute. Toulouse executed the catch and drive close to the Saints' line and Christian Labit emerged from the pack with the ball to score, and Delaigue's conversion gave the home side a 19-6 lead as the break.
Grayson and Delaigue swapped early second-half penalty goals, before Saints captain Budge Pountney and Toulouse centre Cedric Desbrosse were both yellow carded as both sides fought tooth and nail.
Michalak added a penalty to extend their lead, and Toulouse always looked in control, but Saints have proved that, under the guidance of Smith that they have the steel to compete at the highest level.
When replacement Jon Sleightholme scored a well-worked try after 63 minutes, and Grayson's extras narrowed the gap to 25-16.
But when home replacement Cedric Heymans capitalised on a James Brooks error to score untouched under the posts moments later, Toulouse had reasserted their authority, and secured a place in the final four.
Toulouse: Tries - C Labit, C Heymans; Pens - Y Delaigue 4, F Michalak 2; Cons - Y Delaigue 2.
Northampton: Try - J Sleightholme; Pens - P Grayson 3; Con - P Grayson. Halftime: 19-6.
Heineken man-of-the-match: Christian Labit (Toulouse)
Toulouse: C Poitrenaud; E Ntamack (C Heymans 65), C Desbrosse (Y Jauzion), X Garbajosa, V Clerc (C Heymans 39-40); Y Delaigue, F Michalak; P Collazo (B Lecouls 72), Y Bru, J-B Poux, D Gerard (G Lamboley 80), F Pelous (capt), T Brennan (F Maka 56), J Bouilhou, C Labit (W Servat 67).
Northampton Saints: N Beal (J Sleightholme 54); J Brooks, B Reihana, C Hyndman (M Tucker 40), B Cohen; P Grayson, M Dawson; T Smith, S Thompson, M Stewart (C Budgen 46-74), M Lord (M Soden 76), J Phillips (R Hunter 60), M Connors (M Soden 37-40), B Pountney (capt), A Blowers.
Yellow cards: B Pountney (Northampton), C Desbrosse (Toulouse).
Perpignan stunmed the Stradey Park faithful with a 26-19 win over the Scarlets to strut into the Heineken Cup semi-finals.
Man-of-the-match Manny Edmonds scored 13 points for the winners, including two crucial dropped goals in the second half.
'I didn't think I played that well,' Edmonds said after the match. 'I was lucky the forward pack was going so well, and we'll take a lot out of this game.'
Llanelli coach Gareth Jenkins said: 'We just have to reflect on the result. We weren't beaten by a better team, but we were beaten.
'Losing Dafydd upset our lineout, in particular. We put a lot of pressure on ourselves out there and we didn't handle it well. We lacked momentum.'
ERCAUDIO**'Our European Cup campaign has come to an end, and the boys are quite unconsolable' (1 min 33 secs) Llanelli wing Mark Jones CLICK HERE
Perpignan were awarded a penalty try after only 60 seconds when Irish flanker Simon Easterby tackled fullback Jean-Marc Souverbie without the ball on the Llanelli try-line.
Things went from bad to terrible for the home side in the ninth minute when Wales international backrower Dafydd Jones was sent off after only nine minutes for stomping on an opponent's head, reducing the Scarlets to 14 men for the remaining 71 minutes.
They kept in touch through the boot of Stephen Jones, who made a superb break in the 24th minute before offloading to tighthead prop Matryn Madden to score under the posts. It was Madden's fifth Heineken Cup try - only two men have scored more this season.
The Frenchmen hit back with a soft try to Canadian No 8 Phil Murphy to give them a 14-13 lead at the break, and Edmonds extended the lead with two penalty goals at the start of the second half, one of which was cancelled out by Jones.
Edmonds slotted a monster dropped goal on the hour mark, and added another one before Perpignan withstood a lengthy attack on their try-line as Llanelli desperately tried to level the scores and take the match into extra time.