William Gallas scored the only goal just before halftime as Arsenal beat Chelsea to stay at the top of the Premier League table.
Gallas headed home the winner in first-half stoppage time to restore a one-point advantage at the summit for Arsene Wenger's team.
He nodded the ball into an empty net after Chelsea goalkeeper Petr Cech came to try and collect a looping Cesc Fabregas corner, but failed to make any contact.
Arsenal had chances to wrap up victory after the break, but Robin van Persie and Emmanuel Adebayor both had goals disallowed while van Persie and Fabregas both wasted great opportunities.
For Chelsea Andriy Shevchenko failed to trouble Manuel Almunia with a free header, and had a blistering free-kick tipped over by the Arsenal goalkeeper.
The victory was a deserved one for an Arsenal team who looked the brighter outfit for most of the 90 minutes as Chelsea struggled without skipper John Terry who went off with a foot injury in the latter stages of the first half.