Wales are on course for their first Grand Slam since 1978 after a record win over Scotland at Murrayfield.
Tries from Ryan Jones, Rhys Williams, Shane Williams and two from Kevin Morgan gave Wales a 38-3 interval lead.
Rhys Williams added a second after the break, but the game was turned on its head as Andy Craig, Rory Lamont and Chris Paterson crossed for Scotland.
Despite Scotland convincingly winning the second half 19-8, the match had already been decided by half-time.
Wales coach Mike Ruddock will be alarmed at how his side allowed Scotland back into the match in the second half.
But their fourth win of this season's Six Nations campaign was wrapped up in a sensational opening 40 minutes.
Flanker Ryan Jones, celebrating his 24th birthday, started and finished a sensational counter-attack to give Wales a perfect start after four minutes.
He burst through two would-be Scottish tacklers after Wales attacked from deep from a loose Hugo Southwell clearance kick.
Slick passing between Morgan, Gethin Jenkins and Rhys Williams left the home defence in tatters before Martyn Williams delivered the final pass for Jones to run in unopposed.
Scotland looked set to hit back immediately but Dan Parks failed to pick up an overlap, instead seeing his long pass intercepted by Rhys Williams, who raced the length of the field to score.
Worse was to follow for the stunned Scots as a breathtaking passage of play resulted in a Shane Williams try.
Stephen Jones made the decisive midfield break; he passed on to Michael Owen, starting his first game as captain, who had a choice of the two Williams wingers on his left shoulder.
A Chris Paterson penalty got Scotland on the board with the scores at 24-3 but it only briefly curtailed the scoring.
Another missed Scottish tackle, this time by Rory Lamont, allowed Tom Shanklin to pierce the home defence and he off-loaded perfectly to the on-rushing Morgan to score.
There was time for a second Morgan converted try before the interval, created by an electric break from scrum-half Dwayne Peel.
Wales needed just eight minutes to open their account after the break as Peel took a quick tap penalty to send Rhys Williams on his way.
Stephen Jones, who finished with 16 points, then ruined his 100% kicking record by missing his only kick of the afternoon.
Scotland, though, hit back and Andy Craig's try was nothing less than they deserved after their best passage of attacking play all afternoon.
A sweeping move from right to left tied up the Wales defenders, creating a two-man overlap in the corner.
When Wales lock Brent Cockbain was sent to the sin-bin for illegally denying a certain try, a second Scotland try soon followed as Rory Lamont went over on his debut.
With 10 minutes to go, Paterson closed the deficit even further when he collected a Southwell kick ahead for a converted try.
But the contest was long over by then.
Scotland: Paterson, R Lamont, Craig, Southwell, S Lamont, Parks, Cusiter, T Smith, Bulloch, Kerr, Grimes, Murray, Taylor, Petrie, Hogg.
Replacements: Henderson for Craig (76), Ross for Parks (41), Blair for Cusiter (44), Douglas for Kerr (41), Hines for Grimes (41). Not Used: Russell, Dunbar.
Wales: Morgan, R Williams, Shanklin, Henson, S Williams, S Jones, Peel, Jenkins, Davies, A Jones, Cockbain, Sidoli, R Jones, M Williams, Owen.
Replacements: Luscombe for R. Williams (68), Sweeney for Henson (76), McBryde for Davies (50), Yapp for A Jones (63), J. Thomas for Cockbain (71). Not Used: Sowden-Taylor, Phillips. Sin Bin: Cockbain (61).
Referee: Jonathan Kaplan (South Africa)