The champions host Edinburgh

Perennial Welsh hopes Llanelli have home advantage for the first of them against French champions Biarritz.

Saturday sees Edinburgh face the daunting trip to take on champions Toulouse, while Munster host Stade Francais at their Limerick fortress.

The semi-final line-up will be completed on Sunday when Wasps take on Gloucester in an all-English affair.

A packed Stradey Park should ensure a tremendous atmosphere for this meeting between the pride of Wales and the French champions.

But Llanelli have been beaten three times previously by French opposition in the knock-out stages, and home advantage may not necessarily be decisive.

Brusque is a man in form

The Scarlets lost to Perpignan at the same stage a year ago, but having won at Northampton to secure a home tie, they expect to go at least one better this time.

Biarritz have a clutch of internationals - Nicolas Brusque, Serge Betsen, Dimitri Yachvili - in prime form after helping France win the Grand Slam.

And after twice falling at the quarter-final hurdle in the past three seasons, they too will not arrive short of incentives.

Verdict: Scarlets left red-faced

This would appear to be the most straightforward of the four ties, with the defending champions strong favourites to secure a 'home' tie in the semi-finals.

Edinburgh may have shocked the French aristocrats in the first round of pool matches, but Toulouse did not concede a point in the return fixture.

Toulouse opt for Cup switch

Having switched the match from their Stade Ernest Wallon home to the 36,500-capacity Stadium de Toulouse, the hosts will not lack for support.

But they will be handicapped by the absence of first-choice half-backs Fr�d�ric Michalak and Jean-Baptiste Elissalde, even if Yann Delaigue offers experience at fly-half.

Without the injured Simon Taylor, the prospects of Edinburgh - the first Scottish side to reach the quarter-finals - look far from rosy, even with Todd Blackadder at the helm.

Verdict: Toulouse too strong

A contest with a real history to it, given the regularity these sides meet in the Heineken knock-out stages.

Munster prevailed at Thomond Park three years ago at the same stage, before losing by a point to Stade in a semi-final staged in Lille the following year.

Will Munster be celebrating again?

The Parisian heavyweights have had a poor season domestically, and may need to win the tournament to guarantee their involvement next year.

They did rouse themselves to beat an out-of-sorts Leicester at Welford Road to reach the last eight.

But Munster, buoyed by half-a-dozen of Ireland's Triple Crown winners and a prospective Lansdowne Road semi-final, will be a far tougher proposition at their Limerick fortress.

Verdict: Munster on the march

Having seen their status as English champions-elect cruelly plundered by Wasps at Twickenham last year, Gloucester will make sure they show up this time.

An epic forward battle is guaranteed, with Lawrence Dallaglio and Joe Worsley grappling with England team-mates Trevor Woodman and Phil Vickery.

The contest behind the scrum should also be one to savour, with plenty of pace and power on both sides.

Wasps won the Parker Pen Cup last season in addition to the Zurich title, but know a Heineken crown is required if they are to cement their status alongside Leicester and Bath.

Gloucester also hope to join the elite, but like their first Heineken campaign - which ended with semi-final defeat to Leicester in 2001 - may find familiar rivals blocking their path.