Ulster's crucial Heineken Cup quarter-final meeting with Aviva Premiership pace-setters, Saracens, will be refereed by Jerome Garces.
Garces heads an all-French party, his assistant referees being Mathieu Raynal and Cedric Marchat, with Eric Gauzins in the increasingly important role of TMO.
The decisions as to who would officiate in the Heineken Cup and Amlin Challenge Cup quarter-finals followed a meeting of the ERC Match Officials sub-committee which reviewed performances across all relevant tournaments.
An all-Irish quartet will officiate in the ASM Clermont Auvergne v Leicester Tigers clash at Stade Marcel-Michelin. They include Ulster pair David Wilkinson in the capacity of assistant referee and Simon McDowell who will be the TMO.
Alain Rolland is the referee with George Clancy his other assistant.
Leinster's match against the defending champions, Toulon, at Stade Felix Mayol will be handled by the all-English foursome of referee Wayne Barnes, his assistants Greg Garner and Luke Pearce and TMO Graham Hughes.
The Munster v Toulouse clash at Thomond Park will be refereed by Nigel Owens of Wales.
His assistants are fellow-countryman Neil Hennessy and England's JP Doyle, with Derek Bevan in the role of TMO.