A mighty performance by Argentina saw them to a record win over woeful Wales and a first-ever Test series victory.
Argentina (16) 45
Tries: Tiesi (2), JM Fernandez Lobbe
Cons: Todeschini (3)
Pens: Todeschini (8)
Wales (6) 27
Tries: Delve, S Williams, L Byrne
Cons: N Robinson, Hook (2)
Pens: Hook (2)
A near-flawless kicking display from fly-half Federico Todeschini, who claimed 30 points, built the lead.
Gonzalo Tiesi pounced on a charged down James Hook kick for the first try in Buenos Aires, Juan Fernandez Lobbe's try after the break extending the lead.
Gareth Delve and Tiesi scored before late efforts from Shane Williams and Lee Byrne gave Wales' score a gloss.
Added to last week's 27-25 first Test win in Puerto Madryn, the Pumas will be in good heart for next week's visit of New Zealand to the capital's Velez Sarsfield stadium.
We've learnt a lot, that we have to compete physically, have possession and play gain-line rugby
Wales coach Gareth Jenkins
With their leading players back, coach Marcelo Loffreda's side showed surprising adventure from the outset, a move from turnover ball on their own line ending with a third-minute penalty for Todeschini.
Superb sleight of hand from Felipe Contepomi in midfield looked to have sent Martin Durand in for the opening try, but the flanker spurned a huge overlap and was held up over the try line by Williams' outstanding defensive work.
Under pressure beneath his own posts, Ian Evans was sin-binned for killing the ball, Todeschini slotting the penalty.
Contepomi, recalled at 12 after medical exams caused him to miss the first Test, then got the better of rookie opposite number Hook by charging down his clearance.
The ball fell to centre partner Tiesi who touched down a simple try, converted by Todeschini.
Hook, winning his first full cap, got Wales on the scoreboard with a penalty, having missed an earlier chance from 40m.
Todeschini landed a third penalty, but on the stroke of half-time Hook slotted a difficult chance to keep Welsh hopes alive.
Straight after the restart, though, a patient and aggressive Pumas build-up was rewarded.
Rookie lock Ian Evans was sin-binned in the first half
Open-side Fernandez Lobbe took Agustin Pichot's pass in midfield and chose a fine angle to burst through opposite number Gavin Thomas' tackle for the second try.
Todeschini piled on the misery with the conversion and two more long-range penalties.
Dragons tight-head prop Rhys Thomas came on for Adam Jones to win his first cap in the most unhopeful of circumstances.
Just a minute later he saw Hook sin-binned for a high tackle on Todeschini - who quickly got up to land his eighth kick at goal.
Pumas tight-head Martin Scelzo was yellow carded for foul play, at last giving Wales some space to work in.
A sweeping move across the field saw Byrne feed Delve in the corner, and the Bath number eight - a half-time replacement for knee-injury victim Alix Popham - made no mistake to claim his first international try.
But yet another Todeschini penalty was followed by a swift Pumas attack, the forwards drawing in the cover before releasing the three-quarters, Tiesi sent clear in the corner for his second try.
Todeschini's final penalty was followed by an unlikely Welsh revival, a classy break by Hook ending with Williams' try.
As the home side began their celebrations early, Byrne was allowed a late, clear run to the line to make the losing margin closer than it deserved.
Wales had previously lost a non-cap series to Argentina in 1968, but had won the two Tests in 1999 and shared the spoils in 2004.
The heavy defeat leaves the inexperienced squad - missing 21 front-line players - still seeking their first win under new coach Gareth Jenkins.
Argentina: Juan Martin Hernandez (Stade Francais); Francisco Leonelli (Edinburgh), Gonzalo Tiesi (London Irish), Felipe Contepomi (Leinster), Lucas Borges (Stade Francais); Federico Todeschini (Beziers), Agustin Pichot (Stade Francais, capt); Rodrigo Roncero (Stade Francais), Mario Ledesma (Clermont Auvergne), Martin Scelzo (Clermont Auvergne), Ignacio Fernandez Lobbe (Sale Sharks), Rimas Alvarez Kairelis (Perpignan), Juan Martin Fernandez Lobbe (Liceo Naval), Martin Durand (Montpellier), Gonzalo Longo (Clermont Auvergne)
Replacements: Pablo Gambarini (CASI) for Ledesma 75, Marcos Ayerza (Club Newman) for Roncero 73, Manuel Carizza (Biarritz) for I Fernandez Lobbe 64, Martin Schusterman (Plymouth Albion) for Durand 55, Nicolas Fernandez Miranda (Hindu Club) for Pichot 70, Jose Maria Nunez Piossek (Bayonne) for Leonelli 75, Federico Serra (Miras) for Contepomi 73.
Sin Bin: Scelzo (57).
Wales: Lee Byrne (Ospreys); Mark Jones (Scarlets), Jamie Robinson (Blues), James Hook (Neath/Ospreys), Shane Williams (Ospreys); Nick Robinson (Blues), Mike Phillips (Blues); Duncan Jones (Ospreys, capt), Huw Bennett (Ospreys), Adam Jones (Ospreys), Ian Evans (Ospreys), Ian Gough (Dragons), Alun Wyn Jones (Ospreys), Gavin Thomas (Scarlets), Alix Popham (Scarlets).
Replacements: Richard Hibbard (Ospreys) for Bennett 67, Rhys Thomas (Dragons) for A Jones 57, Gareth Delve (Bath) for Popham 41, Matthew Watkins (Scarlets) for J Robinson 34, Andy Williams (Bath) for Phillips 67.
Sin Bin: Evans (18), Hook (55).
Referee: Dave Pearson (England).