AC Milan have lost their first Serie A match since October 2011 as Inter claimed a 1-0 win in the Milan derby.
Alexandre Pato had an early opportunity to give the hosts the lead, but his snatched shot blazed over the crossbar.
As Milan asserted their dominance, Kevin-Prince Boateng's half volley flew off target.
Ricardo Alvarez should have done better for Inter just before half time, but Christian Abbiati got down to save the midfielder's shot with his legs.
The hosts had the final say of the half when Mark Van Bommel's powerful drive crashed back off of the bar.
Milan came out the quicker after the break, but Inter made the breakthrough against the run of play on 54 minutes when Diego Milito fired in after capitalising on Ignazio Abate's error.
Alvarez tried to catch Abbiati out from 30 yards on the hour, but the keeper managed to save.
Substitute Clarence Seedorf almost had an instant impact when his dipping long-rannge effort forced a good save from Inter shotstopper Julio Cesar.
Another Milan substitute, Robinho, nearly found an equaliser in the final 10 minutes, but his poked effort was stopped by the feet of Cesar.
