Lazio finished the millennium two points clear at the top after beating Piacenza 2-0 yesterday while rivals Juventus drew 1-1 with Fiorentina.
Lazio won their afternoon match and then had to wait for Juventus' evening kick-off. Their Christmas box came early in Florence, where Fiorentina went a goal down in the 16th minute to a powerful Igor Tudor header.
But Gabriel Batistuta levelled four minutes later, steering home a cross from Enrico Chiesa, while a second-half header from Chiesa hit the crossbar after a desperate block by goalkeeper Michelangelo Rampulla.
The result left Juventus two behind Lazio, who are confirming pre-season tips as favourites for the title.
Lazio's Chilean striker Marcelo Salas opened the scoring after only nine minutes. Yugoslav defender Sinisa Mihajlovic sent a high ball in to Swiss midfielder Guerino Gottardi and his nod on was driven home by Salas.
It was Lazio's 100th goal of 1999, the best performance by any team in Italy, and the 101st followed 50 minutes later.
Mihajlovic crashed one of his trademark free-kicks against the Piacenza wall, but rifled home the rebound from the edge of the area.
Parma, who started October third from bottom, finished December third from top after beating title rivals AS Roma 2-0 on a pitch which prompted the fury of Roma coach Fabio Capello.
The Serie A's top scorer, Argentinian Hernan Crespo, struck in the third minute to bring his total to 11 this season and Stefano Torrisi drove home a shot from outside the area in the 32nd minute.
Capello was angry that the match had been played, saying: "The match should have been suspended. People talk a lot about professional football, of spectacle and then you go and play on a pitch in conditions like that."
