Chelsea had no difficulties seeing off West Ham, which is still without a point after four matches. Michael Essien netted Chelsea's first goal after two minutes and headed in its third in the 83rd.
Arsenal is two points behind Chelsea in second after routing Bolton 4-1, while big-spending Manchester City was held to a 1-1 draw by Blackburn to collect only one point from its last two matches.
Tottenham was held 1-1 by West Bromwich, as was Sunderland at Wigan, while Blackpool won its second match since being promoted, prevailing 2-0 over fellow newcomer Newcastle.
Fulham's 2-1 victory over Wolverhampton came at a cost, with Bobby Zamora injuring his leg to be ruled out for four months.
Chelsea's fourth straight win never looked in doubt when Essien headed in after two minutes and Salomon Kalou scored with a ricochet from a clearance by defender Matthew Upson in the 18th.
Essien scored Chelsea's third before Scott Parker hit a late consolation goal for West Ham by lobbing goalkeeper Petr Cech.
At Emirates Stadium, Laurent Koscielny scored his first goal for Arsenal in the 24th, but the French defender's poor header allowed Johan Elmander to level just before the break.
Marouane Chamakh restored Arsenal's lead with a 58th-minute header. A tackle from behind on the Morocco striker resulted in Gary Cahill being sent off in the 64th.
Arsenal midfielder Alex Song chipped goalkeeper Adam Bogdan from a tight angle, and substitute Carlos Vela blasted in the fourth from the edge of the area in the 83rd.
While Arsenal successfully overcame injuries to key attacking players, north London rival Tottenham struggled without striker Jermain Defoe and defender Michael Dawson.
And Spurs playmaker Luka Modric limped off injured shortly after pouncing on a loose ball to put Spurs ahead in the 27th. Chris Brunt leveled for West Brom in the 41st with a close-range header.
Man City's hopes of reaching the top four were hit by another setback, leaving the team with only one win from four matches.
Patrick Vieira's 55th-minute goal salvaged a draw against Blackburn, which led through Nikola Kalinic after a mix-up between Kolo Toure and goalkeeper Joe Hart.
At Craven Cottage, Mousa Dembele canceled out Jelle van Damme's 10th-minute opener for Wolves at the start of the second half.
And Dembele scored from a free kick in injury time to clinch Fulham's 2-1 win after Wolves defender Christophe Berra was sent off for receiving a second yellow card.
Sunderland left Wigan with a point despite midfielder Lee Cattermole being sent off against his former club after two poor challenges brought him as many bookings.
Asamoah Gyan put Sunderland ahead on debut after volleying home in the 66th, but Antolin Alcaraz headed in a late equalizer.
At St James' Park, Charlie Adam converted a 45th-minute penalty after Blackpool teammate Luke Varney was tripped by Newcastle midfielder Alan Smith. DJ Campbell sealed the victory in the 90th.