AC Milan went top of Serie A by beating derby rivals Inter Milan 1-0 on Saturday, thanks to an early goal by winger Serginho.
The Brazilian ran on to a defence-splitting pass from compatriot Rivaldo and rounded Inter keeper Francesco Toldo to score in the 13th minute.
The win, in front of a capacity 78,000 crowd at the San Siro stadium, left AC Milan ahead on goal difference from second-placed Juventus, who were held 1-1 at home earlier on Saturday by Bologna.
Inter are in third place. An under-strength Juventus needed an equaliser four minutes from time by Mark Iuliano to draw 1-1 at home to Bologna on Saturday.
After being overshadowed by the Rome derby in recent seasons, the clash of the two Milan giants was back on centre stage with both sides in the hunt this season at home and in Europe.
Milan, who face Real Madrid in the Champions League on Tuesday, were without Portuguese playmaker Rui Costa but opted to replace him with Serginho rather than Ukrainian Andriy Shevchenko, who had to again settle for a place on the bench.
That move may well have been inspired by the decision of Inter coach Hector Cuper to leave his captain Javier Zanetti on the bench after his tiring trip to Japan with Argentina.
His compatriot Nelson Vivas was given the right-back slot and Milan coach Carlo Ancelotti was clearly hoping that Serginho's pace would trouble the former Arsenal defender who has had limited chances this season. The strategy paid off handsomely as Vivas was left exposed by Rivaldo's pass into Serginho's path which led to the goal.
But after that promising start the game became more of a battle than a demonstration of the talent at both coaches' disposal. The early goal put the pressure on Inter to attack but they failed to create enough clear chances to trouble Milan's Brazilian 'keeper Dida.
After the break Milan were content to keep possession and neutralise Inter, whose only attacking approach was to look to Christian Vieri, who in the absence of another jet-lagged Argentine, Hernan Crespo, was partnered by an out-of-sorts Alvaro Recoba.
When Vieri finally did get a chance, after Milan's defence failed to clear a Recoba free-kick, the burly striker somehow fired over from five metres out with just over 15 minutes left.
Then with 10 minutes remaining, Shevchenko was denied a second for Milan when his "goal" was ruled out for pushing. Inter have now failed to win any of their last three games after their home defeat to Udinese and last week's draw at Roma.
Juventus coach Marcello Lippi, whose side face Spain's Deportivo Coruna in the Champions League on Tuesday, opted to leave strikers Alessandro Del Piero and Marco Di Vaio and Dutch midfielder Edgar Davids on the bench and paid the price as his team struggled against Francesco Guidolin's enterprising Bologna side.
Bologna began brightly and had a great chance in just the eighth minute when Renato Olive burst through but screwed his shot wide and then just before the break Giuseppe Signori made a hash of a shot, miskicking from a good position 12 metres out.
The visitors continued to have the better of the game after the break and in the 65th minute Juve 'keeper Gianluigi Buffon was forced into an excellent double save to keep out successive efforts from Julio Cruz and Leonardo Colucci.
But a minute later Buffon brought down Cruz inside the area and Signori strode up to convert the spot kick and put Bologna ahead. Juve then brought on a trio of substitutes, including Del Piero, and one of them Argentine Mauro Camoranesi put over the corner which Iuliano headed home in the 86th minute.
But the champions had a late scare when two minutes into injury time Bologna sub Tomas Locatelli struck the post with a powerful strike.