Ten-man Inter Milan survived a second-half assault by city rivals AC Milan to win 1-0 at the San Siro on Sunday and claim their 50th Milan derby win in Serie A.
Inter and Milan began the match, the 157th to be played between the sides in Serie A, with 49 wins apiece from 156 meetings.
However, it was Inter who emerged with the bragging rights after Argentinian Walter Samuel stunned a large majority of the 73,000 crowd with a fourth-minute winner.
Inter had boosted their title credentials last week and did them no harm by moving up one place up to fourth to sit four points off Juventus and second placed Napoli, who beat Udinese 2-1.
"There were two good points tonight, one was the way we approached this game and the second was how we handled it when we were a man down for the second half," said Inter coach Andrea Stramaccioni.
"We came into this game focused and started aggressively. We got the goal and when Milan came back into it we managed to restricted them in our area."
With only seven goals from seven games the needs of Massimiliano Allegri's AC Milan side are clear, but the coach was once again left lamenting conceding yet another goal from a set-piece.
"We've conceded again from a set-piece and this is something we need to put right," said Allegri.
"Apart from the goal Inter did not create too many chances. We did, and it's a shame we didn't manage to put them away."
Inter striker Antonio Cassano, who moved to Inter in the close season and was the subject of boos and jeers throughout the match, helped create the opener when he won a freekick for an innocuous challenge on the left wing.
Esteban Cambiasso stepped up and sent in a deep cross that evaded the entire Milan defence, including 'keeper Christian Abbiati, and was met at the far post by a diving Samuel.
Five minutes later Inter spurned a golden chance to double their lead when Abbiati somehow gave the ball away to Diego Milito but the Argentine striker dramatically fluffed two chances to beat the Milan 'keeper.
Inter's early lead injected some urgency into Milan and they went on to dominate the opening half, albeit creating only one real scoring chance.
On 36 minutes Dutchman Urby Emanuelson set up Kevin Prince Boateng, who spurned the chance to level when with only Slovenian Samir Handanovic to beat he sent his shot wide from only 15 yards.
Minutes earlier Inter were even gifted another chance when El Shaarawy lost the ball to Uruguayan Walter Gargano and the ball found its way to Milito, with an alert Mario Yepes coming to Milan's rescue.
Inter coach Andrea Stramaccioni replaced Coutinho with Colombian midfielder Fredy Guarin for the start of the second half but was soon reshuffling when Yuto Nagatomo was sent off for handball, having been cautioned in the first half.
Cassano was then replaced by Alvaro Pereira and Allegri signalled his desire to capitalise on their advantage by sending midfielder Robinho on for wingback De Sciglio.
However, despite Boateng, Robinho and Bojan showing promise, Inter were content to soak up the pressure and launch counter-attacks.
When Bojan picked up the rebound from Riccardo Montolivo's long range shot and delivered a deep cross Boateng, at the far post, bicycle kicked his effort over the crossbar.
Allegri replaced El Shaarawy with Giampaolo Pazzini but the Italy striker was found wanting when Robinho's long cross found him unmarked at the far post.
Emanuelson then sent an angled drive just a foot past Handanovic's post and 10 minutes before the whistle Pazzini missed another chance when Robinho headed Boateng's ball back towards goal.
Milan had appeals for a penalty rejected late on after Pazzini had slipped the ball through to Robinho, who tumbled in the area.