AC MILAN 0-1 INTER MILAN
Inter Milan's Diego Milito exploited a mistake from Ignazio Abate to decide the Milanese derby and end AC Milan's 12-match unbeaten run in Serie A.
The Argentine slid the ball past Christian Abbiati after Abate had failed to cut out a crossfield pass.
Former Manchester City striker Robinho squandered two excellent chances, but Milan mostly struggled to carve out clear opportunities to level.
The loss leaves Milan a point off leaders Juventus with Inter in fifth.
The victory is Inter's sixth successive win in Serie A and they now lie just five points off their city rivals despite a dreadful start to the season that left them in the relegation zone in late October.
Nominally the "away" side at the San Siro stadium they share with Milan, Claudio Ranieri's side were unfortunate not to take the lead in the fifth minute when the offside flag was raised after Thiago Motta headed home Maicon's free-kick.
Ricardo Alvarez's shot was then saved by Abbiati from point-blank range, while Mark van Bommel's effort off the bar from the edge of the box was as close as Milan got before the break.
Japanese international Yuto Nagatomo cut in from the left flank and shot straight into Abbiati's midriff as Inter pressed for a second after Milito's strike.
But they rarely looked like needing it before Milan, sparked into life by the arrival of substitute Stephan El Shaarawy, briefly threatened through Brazilian Robinho.