Ireland captain Brian O'Driscoll stretches to score against Wales
Wales 9 (9)
Pens: S Jones 3.
Ireland 19 (12)
Tries: R Best, O'Driscoll, O'Gara.
Cons: O'Gara 2.
Ireland made Wales pay for their mistakes in an open and thrilling RBS Six Nations clash in Cardiff.
Wales had a nightmare start when Brian O'Driscoll blocked Stephen Jones' kick and Rory Best scored after 46 seconds.
The hosts worked their way back through three Jones penalties, but the Irish led at half-time as O'Driscoll dived over in the corner for a converted try.
A third Irish try nine minutes from the end, Ronan O'Gara scoring from close range, ended Welsh hopes of a comeback.
A heavyweight Welsh front-row of Chris Horsman, Rhys Thomas and Gethin Jenkins had been meant to pulverise the Irish scrum, but the visitors never buckled.
Wales' backline had been hampered by a succession of injuries and suspension to their inspirational former captain Gareth Thomas.
One of those to benefit was Chris Czekaj, but the Cardiff Blues wing made a mess of his first Six Nations start to gift Ireland a try in the opening minute.
Fielding a kick from Ireland fly-half O'Gara, Czekaj opted to keep the ball alive rather than let it roll into touch and his pass put Jones under pressure.
The Wales fly-half tried to clear his lines but opposite captain O'Driscoll was already on top of the Llanelli Scarlet to charge the kick down.
Ulster hooker Best gratefully gathered the loose ball to flop over the try line, although O'Gara was unable to make the conversion.
Wales replied admirably with Hal Luscombe, on the right wing, and flanker Martyn Williams making ground against the Irish defence.
The pressure drew a penalty and Jones stroked over an easy three points from in front of the posts.
A Denis Hickie dart down the blind-side of a ruck nearly brought Ireland a second try, but David Wallace was just unable to take the flick pass.
The pace on the game and attacking intent from both sets of backs was thrilling and the noise rolling out from the crowd packed into the Millennium Stadium bore evidence.
O'Gara missed a difficult penalty chance from one Irish foray and then had to watch Jones slot his second to give Wales a 6-5 lead with 19 minutes gone.
Wales' Stephen Jones is tackled by opposite fly-half Ronan O'Gara
That sparked a spell of fierce Welsh pressure that had Ireland rocking and earned Jones a third successful pot at goal.
Hickie spilled blood in the cause and had to go off for stitches to a head wound, with Geordan Murphy temporarily taking his berth on the Ireland left wing.
Wales did not escape either with number eight Ryan Jones suffering a badly cut eye that needed five stitches, Gavin Thomas filling the ranks for a spell.
Back came Ireland through Murphy, who gathered his own huge Garryowen in the Wales 22.
Wallace bust through a couple of Welsh tackles to suck in the cover and O'Gara fired a long pass for O'Driscoll to score his 17th championship try in the right corner.
O'Gara had been having a poor afternoon up to that point, but the vision of his pass for the try and then an excellent conversion redeemed the Munster man.
Ireland started the second half with that slim 12-9 lead but were fortunate not to lose that advantage soon after the restart.
Czekaj broke clear down the left, sending a grubber past Andrew Trimble and seemed destined to gather and score.
But Simon Easterby clipped the Blues wing just enough to slow him, the infringement going unpunished, allowing Ireland full-back Girvan Dempsey to get back and slap the ball away.
It is a feeling of frustration, we got the effort and intensity we wanted but we didn't have the edge
Wales coach Gareth Jenkins
Aled Brew came on to make his Wales debut for the injured Luscombe and with his first touch made good ground on the right wing.
The rookie Wales midfield partnership of Jamie Robinson and James Hook had largely held their own against the vaunted O'Driscoll and Gordan D'Arcy pairing.
Hook was wide with a snap drop-goal that would have brought Wales level after 63 minutes.
But the Ospreys youngster then had a kick charged down by O'Gara that led to the Munster fly-half claiming a decisive third Ireland try.
D'Arcy made the decisive break, brushing through Czekaj too easily to get to within inches of the Welsh line and O'Gara was on hand to dive over despite Hook's despairing tackle.
Wales drove forward in search of a try but excellent Irish defence, with Denis Leamy outstanding, ensured it was their Grand Slam and Triple Crown hopes that remain alive.
Eddie O'Sullivan's men can now look forward to a home game against France at Croke Park in a week's time.
But they may have to do it without O'Driscoll, who is a doubt after limping off with a hamstring strain at the end of the match in Cardiff.
Wales, meanwhile, must gather themselves for a trip to face Scotland at Murrayfield next Saturday.
Wales: K Morgan; Luscombe, J Robinson, Hook, Czekaj; S Jones (capt), Peel; G Jenkins, R Thomas, Horsman, Gough, Wyn Jones, Popham, M Williams, R Jones.
Replacements: Brew for Luscombe (60), Phillips for Peel (73), Rees for R. Thomas (67), D. Jones for Horsman (55), Sidoli for Gough (71), Gavin Thomas for R Jones (34-40) and for Williams (79), Not Used: Sweeney.
Ireland: Dempsey; Trimble, B O'Driscoll (capt), D'Arcy, Hickie; O'Gara, Stringer; Horan, R Best, Hayes, O'Callaghan, O'Connell, S Easterby, D Wallace, Leamy.
Replacements: G. Murphy for Hickie (27-37) and for B. O'Driscoll (75), Flannery for R. Best (65). Not Used: S. Best, N. Best, M. O'Driscoll, Boss, P. Wallace.
Referee: Kelvin Deaker (New Zealand).