Eidur Gudjohnsen scored a late winner to deny valiant Huddersfield a replay after an entertaining FA Cup tie.
Carlton Cole put Chelsea ahead with a header after his initial shot had looped upwards after being blocked.
Gary Taylor-Fletcher, who saw a great chance saved in just the second minute, equalised with a well-taken right-foot shot 15 minutes from time.
But Gudjohnsen struck after ghosting into the penalty area and connecting with Arjen Robben's precise pull-back.
Huddersfield manager Peter Jackson had asked his players to give a good account of themselves and he can be proud of their effort and ambition, trying to get the ball down and play football whenever possible.
But for large periods Town were unable to cope with the pace of the game and Chelsea's movement.
The likes of John Terry, Frank Lampard and Hernan Crespo might have been rested but Jose Mourinho's team was still packed with internationals.
Damien Duff, Joe Cole and Shaun Wright-Phillips were at times on another planet, easing past opponents at will and slicing open the Town defence with their pace and trickery.
But for all that Taylor-Fletcher should have given Town the lead in just the second minute.
Robert Huth cut out a low cross but only succeeded in deflecting the ball to Taylor-Fletcher, who failed to execute a clean strike despite finding himself in the short of space rarely afforded Chelsea opponents 10 yards from goal.
Chelsea then found their range and created several openings before their 12th-minute opener.
Holding midfielder Lassana Diara, impressive on his full debut, had a long-shot saved, as did Duff after the Irishman had cut inside before shooting from 18 yards.
Town were a little unfortunate over Chelsea's opener, Carlton Cole heading past Phil Senior after his initial shot had been blocked by Martin McIntosh and looped straight up in the air.
Cole spent much of the previous two seasons on loan at Charlton and Aston Villa - and the header was his first goal for the Blues since April 2003.
But if the away fans feared an avalanche of goals it failed to materialise, with Huddersfield keeping the Premiership leaders out for a further 70 minutes.
Chelsea might have added to their lead before the break but Wright-Phillips twice shot wide from 18 yards, Carlton Cole was denied by a superb finger-tip save from Senior and a Huth header rebounded off the crossbar.
Huddersfield started to mount some kind of threat after the break, Nathan Clarke and McIntosh both shooting wide from distance.
And with 15 minutes left Taylor-Fletcher struck, running on to a superbly weighted pass from substitute Michael Collins before shooting past Carlo Cudicini, who got a hand on the ball but could not prevent the equaliser.
Huddersfield remained on level terms for seven minutes before substitute Robben marauded down the left before picking out an unmarked Gudjohnsen to score.
Chelsea: Cudicini, Johnson, Ricardo Carvalho, Huth, Bridge (Del Horno 77), Wright-Phillips (Paulo Ferreira 77), Joe Cole, Diarra, Gudjohnsen, Duff (Robben 72), Carlton Cole.
Subs Not Used: Pidgeley, Nuno Morais.
Booked: Carlton Cole.
Goals: Carlton Cole 12, Gudjohnsen 82.
Huddersfield: Senior, Holdsworth, Nathan Clarke, McIntosh (Mirfin 77), Adams, Brandon, Hudson, Ahmed (Tom Clarke 45), Schofield (Collins 63), Abbott, Taylor-Fletcher.
Subs Not Used: Rachubka, McAliskey.
Goals: Taylor-Fletcher 75.
Ref: A Wiley (Staffordshire).