Argentina (13) 19
Longo's try gave Argentina breathing space in Paris
Cons: F Contepomi
Pens: F Contepomi (3)
Scotland (6) 13
Pens: Parks, Paterson
Argentina powered their way into the semi-finals of the World Cup for the first time after winning a war of attrition with Scotland in Paris.
The Scots went ahead with a monster penalty from Dan Parks, but Felipe Contepomi replied twice for the Pumas.
Gonzalo Longo then charged down a Parks kick and pounced on the loose ball to score and give Argentina control.
Chris Cusiter squirmed over in reply for Scotland after the break, but the Pumas held on for a nervous victory.
Argentina, who also reached the quarter-finals in 1999, will now face South Africa in the semi-final in Paris next Sunday.
And defeat for Scotland meant there will be no Six Nations treble following surprise wins for England and France on Saturday.
Both sides went into the game unchanged, but the Argentines had been more impressive in disposing of Ireland in their last match than the Scots were in a stuffy win over Italy.
Fly-half Hernandez (right) was instrumental for Argentina
And, while both sides traded high up and unders during a cagey opening, it was the Pumas who made the better catches and the greater ground when the passes started to flow.
However, fly-half Juan Martin Hernandez missed a drop-goal attempt, while Contepomi sliced wide a penalty.
And, from the restart, an Argentine infringement gave Parks an opportunity of his own.
The fly-half's kick from just inside the opposition half crept over the crossbar to put the Scots in front.
Scotland had to withstand a series of Argentine attacks and eventually conceded a penalty after a high tackle on Hernandez by Nathan Hines.
Contepomi made no mistake this time from straight in front of the posts to level the scores.
And the Pumas went ahead after 28 minutes when he kicked from a tighter angle after Rory Lamont was trapped after hesitating while calling for a mark that the referee failed to award.
It got worse for Scotland when Parks' kick was charged down by Longo and the number eight won the race for the ball that squirmed towards the try line.
Contepomi's conversion put Argentina in control, but Chris Paterson maintained his 100% record with the boot as Scotland replied by winning a penalty in front of the posts.
However, the Scots conceded another penalty within seconds of the restart for an infringement in the ruck and Contepomi slotted over a simple kick.
Replacement Andy Henderson won a penalty for Scotland, but Parks fluffed his long-range effort.
And Hernandez made it 19-6 after 54 minutes when his own superb kick for touch gave him room for a fine drop-goal.
Scotland surged back into the game when replacement scrum-half Cusiter finished off in the corner after a thrilling passing move.
The Scots piled forward in search of another score and looked likely to craft a patient forward try before Parks' ill-founded cross kick went straight into touch-in-goal with about a minute left.
They were given one final chance to score when the experienced Pichot tried to run down the last seconds in his 22, only to concede a late scrum.
But a Scotland knock-on heralded the final whistle to shatter their dreams and kick-start the Argentine party.
Argentina: Corleto, Borges, M. Contepomi, F. Contepomi, Agulla, Martin Hernandez, Pichot, Roncero, Ledesma, Scelzo, C. Fernandez Lobbe, Albacete, Ostiglia, J. Fernandez Lobbe, Longo Elia.
Replacements: Senillosa for M. Contepomi (67), Hasan for Scelzo (57), Kairelis for C. Fernandez Lobbe (51), Leguizamon for Ostiglia (55). Not Used: Basualdo, Fernandez Miranda, Todeschini.
Scotland: R. Lamont, S. Lamont, Webster, Dewey, Paterson, Parks, Blair, Kerr, Ford, E. Murray, Hines, Hamilton, White, Hogg, Taylor.
Replacements: Southwell for R. Lamont (68), Henderson for Dewey (41), Cusiter for Blair (56), Smith for Kerr (56), S. Lawson for Ford (68), MacLeod for Hamilton (56), Brown for Hogg (56).
Ref: J Jutge (France).