Llanelli Scarlets struck with two quickfire tries at Stradey Park to come from behind against the Cardiff Blues.
Scarlets: (10) 32:
Tries: Madden, M Jones, King, Watkins, Peel.
Cons: Bowen 3.
Blues: (3) 13:
Tries: M Williams.
Pens: Warren 2.
Despite controlling much of the match, the Scarlets found themselves behind early in the second half after Martyn Williams went over for the visitors.
But scores from Regan King and Matthew Watkins within two minutes of each other transformed the match.
Dwayne Peel's late try gave the final scoreboard a gloss, adding to earlier tries by Martyn Madden and Mark Jones.
The game began badly for the Blues, as a series of blunders saw the home side cross the try line within two minutes.
First Nicky Robinson slipped as he received a pass in his own 22, then from the resulting ruck a wayward pass gave Marc Stcherbina little option but to concede a five-metre scrum.
The Blues pack was turned under pressure and from the resulting quick tap-penalty prop Madden was shunted over for an unconverted try.
Robinson missed a penalty opportunity that would have got the Blues on the scoreboard and did not last the first half, being replaced by Roger Warren after taking a knock.
It was not long before the Scarlets struck again, as wing Mark Jones did his hopes of a Wales recall no harm at all with a fine try.
Jones rounded opposite wing Craig Morgan far too easily, then chipped over Blues full-back Rhys Williams for an excellent solo score.
Unfortunately for the Scarlets, fly-half Gareth Bowen was again wide with the conversion and a Warren penalty reduced the home side's lead to 10-3.
With Bowen missing a late penalty - his third failure with the boot - the Scarlets had just that seven-point lead at the break despite controlling the first half.
Warren's second penalty reduced that slim advantage even further soon after the restart, before the Blues stunned Stradey Park by taking the lead.
Referee Nigel Owens sin-binned Wales flanker Dafydd Jones for killing the ball and the Blues took immediate advantage up front as Martyn Williams rolled over from a maul, with Warren converting.
Staring a hurtful home defeat in the face as the game entered its last quarter, the Scarlets ripped through the Blues twice in two minutes.
First Alix Popham ducked under Andy Powell's attempted smother tackle to send King over, then a kind bounce allowed Mark Jones to gather a kick on the wing and ship a pass inside that saw Watkins scamper half the length of the field.
Bowen finally found his range to slot the two easy conversions and from being behind the Scarlets had a match-winning 24-13 lead - with a bonus point in the bag for the fourth try.
If there was any doubt that the Blues were beaten, Martyn Williams was sin-binned for a cynical block on Dwayne Peel.
Bowen converted that penalty and then a conversion as Peel squirted over to give the scoreboard a lop-sided look given how close much of the match had been.
Scarlets wing Mark Jones:
"The forwards set the tone today and I was just glad to contribute to the performance with a try.
"I was pleased to get over the whitewash and I got a bit of a lucky bounce with the chip.
"I've had a tough 18 months with injury where I thought I might not play again, but I'm getting there although I'm not the finished article."
Blues coach Dai Young:
"The Scarlets played really well, they won the contact area and they took their opportunities.
"They probably only blew one try-scoring opportunity all game and we struggled against that.
"At one stage when we did edge in front I thought perhaps the picture could have been different, but I have no complaints about the result."
Scarlets: Lee Byrne; Dafydd James, Matthew Watkins, Regan King, Mark Jones; Gareth Bowen, Dwayne Peel; Martyn Madden, Matthew Rees, John Davies, Inoke Afeaki, Chris Wyatt, Dafydd Jones, Simon Easterby (capt), Alix Popham.
Replacements: Craig Dunlea for Madden (62), Adam Jones for Wyatt (62). Not used: Craig Hawkins, Jon Mills, Clive Stuart-Smith, Mike Hercus, Barry Davies.
Blues: Rhys Williams (capt); Craig Morgan, Jamie Robinson, Marc Stcherbina, Jonah Lomu; Nicky Robinson, Ryan Powell; Gethin Jenkins, Rhys Thomas, Martin Jones, Craig Quinnell, Robert Sidoli, Andy Powell, Martyn Williams, Xavier Rush.
Replacements: John Yapp for Jones (70), Duane Goodfield for Thomas (80), Deiniol Jones for Sidoli (57), Robin Sowden-Taylor for Powell (73), Wayne Evans for Warren (74), Tristan Davies for R Williams (70), Roger Warren for N Robinson (30).
Referee: Nigel Owen (WRU).