Italy 4-0 Wales Filippo Inzaghi's hat-trick sends Italy to the top of Group 9.
Italy knew how important a victory was for them and began at a rate of knots. Del Piero was a clear threat and Gianluca Zambrotta was also a danger on the left, Christian Vieri - who had passed a late fitness test on his knee - heading over from one of his crosses on 17 minutes.
The visitors had a chance on the half-hour but John Hartson shot over after Ryan Giggs's cut-back. However, in the last ten minutes of the half Italy seemed destined to score only to be frustrated every time.
First, Inzaghi had a shot deflected away by the alert Mark Delaney, then the same player received the ball five metres out, only for his effort to be smothered and hooked behind by Robert Page. Finally, Paul Jones produced a great save to tip Vieri's dipping effort on to the bar.
There was little change in the early minutes of the second half as Italy continued to push - and Wales's luck appeared to be holding when Cristiano Zanetti hit the outside of the post with a long-range shot. Massimo Oddo was introduced on the right for Italy and finally the breakthrough came a minute before the hour.
Del Piero crossed for Vieri, who shot against the crossbar from close range, but Inzaghi was following up to score. Four minutes later it was 2-0 as Oddo crossed from the right and Inzaghi turned the ball in. Inzaghi did not have to wait long for his hat-trick as on 70 minutes Vieri crossed from the left, Mauro Camoranesi headed on and the AC Milan striker placed the ball underneath Jones.
Not long afterwards, Inzaghi was taken off to a standing ovation, but that did not stop the goals as, on 76 minutes, Simon Davies tripped Zambrotta in the box, allowing Del Piero to roll in the penalty.
The home side played out the rest of the game as an exhibition, knowing the real test will come on Wednesday in Serbia and Montenegro. Wales, now a point behind, face Finland in Cardiff, but will be without Craig Bellamy, Mark Delaney and Robbie Savage, as all were booked and will be suspended.