Ireland will head to Twickenham next Saturday with a Triple Crown and first Six Nations title in their sights after repelling Scotland in Dublin.
They dominated territory and possession in an attritional contest but could not breach the visitors' superb defence.
Instead the hosts had to rely on the boot of Ronan O'Gara, who kicked five penalties to three from Chris Paterson.
Ireland led 12-9 at half-time, and O'Gara landed one more penalty after the interval to seal a deserved win.
Scotland remained in it right to the end as O'Gara missed another penalty with a minute to go, but the visitors can have no complaints with the outcome.
They will head to Rome hoping to conclude an otherwise excellent campaign on a victorious note.
After a downpour just before kick-off, Ireland started at a tremendous pace and were 3-0 to the good in the second minute as O'Gara kicked an easy penalty.
The fly-half rewarded another sustained series of attacks five minutes later with his second but Scotland were given three cheap points from the resultant kick-off as Malcolm O'Kelly impeded Jason White and Paterson opened his account.
The Scotland wing soon levelled the scores for another Irish offence as both sides, particularly the visitors, kicked most of their possession in the tricky conditions.
Ireland looked the more dangerous with ball in hand though, and after Geordan Murphy had entered the line to good effect, O'Gara - who had just pushed another effort wide - kicked them back in front.
But Paterson replied in kind to bring the visitors level again after 27 minutes as the rain started to fall.
Scotland briefly enjoyed some pressure of their own only for Murphy to recover his own fumble from a kick through to the Irish line and launch a breakaway.
Brian O'Driscoll tries to find a way past a resilient Scottish defence
Ireland continued to build the phases to good effect despite Scotland's sterling defence, and O'Gara's fourth penalty gave them a slender half-time advantage.
The Scottish line-out, until this season one of their chief weapons, again floundered on the resumption, allowing Ireland to dominate territory.
The hosts should have scored a try after 48 minutes but Murphy's low pass to Andrew Trimble allowed Hugo Southwell the split-second he needed to bundle the wing into touch.
Again Ireland pressed, only for Sean Lamont to pluck Paul O'Connell's pass out of the sky a metre from the line.
Captain Jason White tried to lift the siege with a thumping hit on Ireland hooker Jerry Flannery, and the hosts' only reward for 15 minutes' dominance was another O'Gara penalty.
Scotland sent on reinforcements in the shape of prop Craig Smith, hooker Dougie Hall and half-backs Chris Cusiter and Gordon Ross.
As the game started to break up, Murphy tried to weave his way through but the Scots' defence remained resolute.
With seven minutes left, the visitors made almost their first foray of the half into Ireland's 22 but whereas their line-out was precarious, Ireland's remained solid.
There was still time for O'Gara to miss a final penalty attempt, but ultimately it made no difference.
Ireland: Murphy; Horgan, B O'Driscoll (capt), D'Arcy, Trimble; O'Gara, Stringer; Horan, Flannery, Hayes; O'Connell, O'Kelly; Easterby, Wallace, Leamy.
Replacements: R Best, S Best, O'Callaghan, M O'Driscoll, Reddan, Humphreys, Dempsey.
Scotland: Southwell; Paterson, Di Rollo, Henderson, Lamont; Parks, Blair; Kerr, Hall, Douglas; Hines, Murray; White (capt), Taylor, Hogg.
Replacements: Lawson, Smith, Kellock, Petrie, Cusiter, Ross, Webster.
Referee: Stuart Dickinson (Australia)