Leinster will play the Glasgow Warriors in the RaboDirect Pro12 play-offs next week in Dublin as the Irishmen finished their regular season on top of the table with an 18th league victory - a 22-18 win at Newport Gwent Dragons.
A try from prop Jack McGrath and points from the boot of fly-half Ian Madigan saw Leinster home.
Flanker Dan Lydiate and Will Harries scored consolation tries for the Dragons at the end, adding to a couple of Lewis Robling penalties and a conversion from replacement centre Adam Hughes. However, neither side had a great deal to play for as Leinster had already booked their play-off place as league leaders and the Dragons could only finish mid-table at best.
The Ospreys warmed up for the play-offs with a hard-earned 18-11 victory over Aironi in Italy.
Knowing their season had already been extended, there was little pressure on the Welsh side, but they still rose to the occasion and produced a win that gives them some momentum heading into the play-offs.
On a tight night, the boot of Dan Biggar proved decisive, as he kicked two penalties and also converted one of his side's two tries which were scored by Richard Fussell and Hanno Dirksen.
Munster wrapped up the regular season with a 36-8 bonus-point home win over a weakened Ulster side.
Simon Zebo and forwards Peter O'Mahony, Mike Sherry, Stephen Archer and Tommy O'Donnell all crossed for the defending league champions, who will travel to the Ospreys in next weekend's semi-finals.
However, the Thomond Park success was marred by a suspected knee injury which forced Paul O'Connell off midway through the second half.