Paris - Two-time European champions Munster went top of Pool 6 on Sunday after an impressive 36-8 demolition of previous tabletoppers Perpignan in Limerick.
Munster have a two-point lead over English outfit Gloucester, who beat Edinburgh 23-12 in Scotland.
Perpignan are third on six and Edinburgh on four with three games remaining.
Munster took the game by the scruff of the neck from the start and by the 35th minute were 22-0 up having scored three tries, the last one a scintillating 45-metre solo effort by Irish international Keith Earls down the right wing.
Flanker Sean Dougall had scored the opener which had stemmed from a poor clearance kick by James Hook, Irish scrum-half Conor Murray producing a lovely off-load in the move that led to Dougall touching down.
Prop Dave Kilcoyne added the second barrelling over from a short distance out.
Perpignan's half was summed up when Hook sent a relatively easy penalty chance well wide of the posts on the stroke of half-time.
Hook, though, did land a penalty early in the second-half as Perpignan tried to get back into the match and become the first French side to win at Thomond Park in the tournament's history.
Not such good news for the Irish side was that neither of their halfbacks lasted long in the second-half, Murray going off and having his right knee placed in a knee brace while fly-half Ian Keatley also trooped off rather gingerly.
Perpignan thought they had scored a try of their own in the 56th minute but Luke Charteris's pass was adjudged to have gone forward.
The hosts got what could prove to be a crucial bonus point in the 65th minute when the referee awarded them a penalty try when Kisi Pulu committed a professional foul in trying to stop them going over. He was sin-binned for his actions and replacement fly-half JJ Hanrahan converted for 29-3.
Munster No8 James Coughlan added a fifth try three minutes from time which Hanrahan also converted and although Joffrey Michel scored a consolation try for Perpignan the French side will need to raise their game considerably for next weekend's rematch.
However, man-of-the-match Earls admitted that his side too needed to improve in certain areas, which fortunately for them they had not been punished by a lacklustre Perpignan side.
"I think we need to improve another 30 percent," said the 26-year-old. "Defensively we were caught out, myself on two occasions, so we have some work to do.
"It will be a tough task in France but we got a good result there two years ago."