Hernan Crespo and Damien Duff scored their first Chelsea goals as the Blues triumphed emphatically at Wolverhampton Wanderers and climbed into top spot.
Frank Lampard and Jimmy Floyd Hasselbaink struck in the first half and Duff made it 3-0 after the break. Crespo then added further gloss to the scoreline with a brace.
Chelsea moved into first place on goal difference, ahead of Arsenal, although the Gunners reclaimed the lead the following day.
Wolves remained at the foot of the table with one point.
Michael Owen’s winner deep into stoppage-time gave Manchester United a dramatic derby victory over Manchester City at Old Trafford.
Wayne Rooney put United ahead after only two minutes, but City responded through Gareth Barry.
While Darren Fletcher twice restored the hosts' lead after the break, Craig Bellamy hit back for the visitors both times, his second leveller coming in the 90th minute.
But in the sixth minute of stoppage-time Ryan Giggs, who had set up Fletcher's goals, released Owen and the striker finished clinically past Shay Given.
The result ended Man City's winning start to the season and left them fourth with 12 points, two places and three points behind Man United, who were in turn three points off the top.