Helped by their returning internationals, Munster won the battle of Ireland's champion sides as three second half penalties from Ronan O'Gara saw them edge Ulster.
MAGNERS LEAGUE: Saturday, September 30
MUNSTER 21 ULSTER 13, Musgrave Park (Att: 5,674)
Scorers: Munster: Tries: David Wallace, Anthony Horgan; Con: Ronan O'Gara; Pens: O'Gara 3
Ulster: Try: Paul Steinmetz; Con: David Humphreys; Pens: Humphreys 2
The Heineken Cup holders overcame a slow start - they were 10-0 down inside seven minutes - to gain only their second win of the season and some long-awaited momentum in the Magners League.
Before the kick-off, it was second from the top playing second from the bottom and the table positions rung true as following a David Humphreys penalty after 93 seconds, Isaac Boss flicked an inside pass for former All Black Paul Steinmetz to dart in under the posts.
Humphreys added the extras and the visitors, who did the double over Munster last season, had the ideal platform to record their fourth win in five outings.
But Munster, as they traditionally do, dug their heels in and faced with a catalogue of bad luck - hooker Frankie Sheahan cried off with a hamstring injury forcing temporary signing Andy Kyriacou to start, while back line trio Christian Cullen, Shaun Payne and Anthony Horgan all sustained injuries during a ferocious 80 minutes - they played to their strengths.
O'Gara's boot and their magnificent maul did the business as Ulster's early exuberance was quashed. After successive lineout mauls on the 20-minute mark, flanker David Wallace plunged over the Ulster line amid a spate of fisticuffs.
Ulster's stand-in captain Justin Harrison squared up to Donncha O'Callaghan and after O'Gara's conversion, the former Wallaby was sin-binned for his overzealousness at the breakdown.
With tempers cooled, Munster clambered into the lead on 27 minutes when a superb pick-up from Trevor Halstead saw the red tide rampage forward and Peter Stringer's long pass to the right put Horgan scampering in.
Munster remained in front until Humphreys punished O'Callaghan for not rolling away in the tackle with his second penalty, and Mark McCall's men took a 13-12 lead into the break.
...Munster's Alan Quinlan is beaten to a lineout ball by Ulster number eight Roger Wilson...
The second half was a slow burner, both sides struggled to retain possession and further injuries - worryingly for Ireland coach Eddie O'Sullivan, Ulster were forced to haul off Tommy Bowe with a suspected thigh injury - disrupted the game.
O'Gara kicked the hosts, who had struggled with their lineout, into the lead on 52 minutes after Bowe had failed to release on the deck, and while Horgan's injury prompted Declan Kidney to summon flanker Tim McGann out to the right wing, Munster's defence allowed them to push on.
Inspired by the lively Boss, Ulster came to the fore just after the hour mark, but nothing came of a flurry of attacks and two further O'Gara kicks, the first after Kieran Campbell was penalised and then yellow carded for blocking Kelly when he was chasing a kick through, handed Munster a morale-boosting win.
Munster: Christian Cullen; Anthony Horgan, John Kelly, Shaun Payne, Ian Dowling; Ronan O'Gara, Peter Stringer; Marcus Horan, Andy Kyriacou, Federico Pucciariello, Donncha O'Callaghan, Paul O'Connell (capt), Alan Quinlan, David Wallace, Anthony Foley.
Replacements used: Trevor Halstead for Cullen (9 mins), Eoghan Hickey for Payne (40+1), Tim McGann for Horgan (55), Timmy Ryan for Pucciariello (80), Mick O'Driscoll for Foley (80+3). Not used: Frankie Roche, Brian O'Meara.
Ulster: Bryn Cunningham; Tommy Bowe, Paul Steinmetz, Paddy Wallace, Andrew Trimble; David Humphreys, Isaac Boss; Justin Fitzpatrick, Rory Best, Bryan Young, Justin Harrison (capt), Matt McCullough, Neil Best, Neil McMillan, Roger Wilson.
Replacements used: Stephen Ferris for N Best (53 mins), Kieron Dawson for McMillan (58), Tim Barker for McCullough (63), Kevin Maggs for Steinmetz (64), Kieran Campbell for Bowe (65), Paul Shields for R Best, Declan Fitzpatrick for Young (both 79), Young for J Fitzpatrick (80+6).
Referee: Donal Courtney (Ireland)
Touch Judges: Eanna O'Dowd, John Carvill (both Ireland)