Leinster inched ever closer to the Magners League title after picking up arguably their most important win of the season at the RDS.
Felipe Contepomi kicked Munster out of the title race as he landed six penalty goals from eight attempts in this niggly inter-provincial clash.
Jonathan Sexton topped off the win with a late drop goal as the league leaders put 12 points between them and the second-placed Cardiff Blues in the standings.
Worryingly for Munster, with their Heineken Cup semi-final trip to Saracens just a fortnight away, half-backs Ronan O'Gara and Peter Stringer both picked up injuries.
O'Gara did not return for the second half after injuring himself at a ruck, while Stringer had to stretchered off in a neck brace after his team-mate Anthony Foley accidentally caught him with an elbow.
Leinster made a business-like start with Contepomi popping two penalties through the posts inside six minutes.
Munster showed plenty of fire but it was the Leinster pack who exerted more control in the tight exchanges and their aggressive defence and work around the fringes knocked the visitors off their stride.
Leinster had an extra week's preparation for this game and Michael Cheika had them primed - they even had a Munster-like lineout maul which gained 20 metres for them.
Leinster ended the first quarter with a 9-0 lead as Contepomi landed his third penalty success after a John Hayes scrum infringement.
Two penalties in the space of six minutes, with O'Gara the scorer, got Munster back in contention. The second came after illegal use of the boot from Malcolm O'Kelly.
The best move of the first half followed when Leinster launched a rapier-like thrust towards the Munster line. The side-stepping Sexton was involved twice and prop Stan Wright, who put in immense work, also got on the ball before Rob Kearney was superbly bundled into touch by Doug Howlett at the corner flag.
But Leinster did manage to stretch their lead in injury time when a soft penalty award allowed Contepomi make it 12-6 at the break.
O'Gara's replacement Paul Warwick notched a confidence-building penalty kick, four minutes after the resumption.
However, Contepomi kicked the second of two quick penalty attempts, after Donncha O'Callaghan had infringed at a ruck, to keep the home side ticking.
Stringer's injury halted play and took the sting out of the match for a while, yet Munster, boosted by Paul O'Connell's introduction, soon found an extra gear.
Two busts forward from Ian Dowling got Declan Kidney's men up to the Leinster 22 and a jinking run from Howlett also tested Leinster's mettle out wide.
A try never came and Warwick's second penalty hit proved to be Munster's final score.
Had Dowling spotted Howlett coming through on a great angle in the 66th minute, the All Black might have touched down but the wingers failed to link up and Leinster ruthlessly closed out the win.
Contepomi nailed his sixth penalty from eight attempts after Munster centre Rua Tipoki had been sin-binned for a neck-high challenge on Luke Fitzgerald.
Sexton added the icing with a smartly struck drop goal and with the young out-half punching the air with delight, Leinster could be just a game or two away from their second league crown.