Munster produced arguably the stand-out performance of the European season to date as they crushed French Champions Perpignan 37-14 at the Stade Aime Giral.
Perpignan were previously unbeaten in Europe on home soil for 16 matches and a staggering five years but Munster showed just how far the Magners League has come with a stunning display of international-class rugby.
Denis Fogarty, Denis Hurley, Jean de Villiers and Dough Howlett crossed for the visitors, who recorded a vital try-scoring bonus point that sees them consolidate their position at the head of Pool 1.
Fellow Irish giants Leinster were also in superb form in Round 4 as they hammered the Scarlets 39-7 at the RDS.
Micahel Cheika's men made it three bonus-point wins in succession following a comprehensive victory in Brive and an equally comfortable triumph at the Parc y Scarlets nine days ago.
Elsewhere, Edinburgh kept their hopes of quarter-final qualification alive with a 9-6 victory over 1998 winners Bath at Murrayfield, while the Ospreys cemented top spot in Pool 3.
Scott Johnson's men were easy winners for the second week running against Italian side Viadana at the Liberty Stadium as they maintained their unbeaten run in this year's European Cup.
Munster, Ospreys and Leinster are all in good positions to qualify for the knockout stages ahead of the final two rounds of action next month, while Cardiff Blues, Edinburgh and Ulster still have a realistic chance of making it through to the last eight.
The Blues were unable to back up their Round 3 victory over European giants Toulouse when they travelled to France on Saturday but Dai Young's men are still in the running in a hugely competitive pool. And with pool leaders Toulouse still having to visit Sale, and Sale having to come to Cardiff, the Blues' chances of repeating last season's semi-final berth are far from over.
Ulster went down to Stade Francais in Paris a day after snow prevented the two sides from meeting at their scheduled venue in Brussels, while the Dragons lost out to unbeaten Biarritz in Llanelli after their game was moved from Rodney Parade because of the adverse weather.
Glasgow couldn't repeat their previous week's win against Gloucester at Kingsholm but one Magners League side did do the double over English opponents.
Connacht secured a 19-7 victory over Worcester at The Sports Ground having already returned from Sixways with four points in Round 3. Connacht remain top of their Amlin Challenge Cup group ahead of French side Montpellier, with Michael Bradley's side in line for another quarter-final appearance in his final season in charge.
Heineken Cup results involving Magners League sides
Edinburgh 9-6 Bath
Leinster 39-7 Scarlets
Newport-Gwent Dragons 8-26 Biarritz
Ospreys 45-19 Viadana
Toulouse 23-7 Cardiff Blues
Gloucester 19-6 Glasgow
Perpignan 14-37 Munster
Stade Francais 29-16 Ulster
Amlin Challenge Cup
Connacht 19-7 Worcester Warriors
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