Brazil midfielder Ramires scored twice as Chelsea got their Champions League Group E campaign back on track with a 4-0 demolition job on Steaua Bucharest at the National Arena.
Slick-passing Chelsea, surprisingly beaten at home 2-1 by Swiss club Basel last month, dominated from start to finish and could have won by a bigger margin.
"We played good football with intelligence and maturity away from home," manager Jose Mourinho told Sky Sports television.
"I think we are going to do it (qualify for the knockout stages). This result today is important because we had to win."
Chelsea and Basel have three points from two games while Steaua are bottom of the group on zero.
Schalke 04, who won 1-0 at Basel on Tuesday, have a maximum six points.
Mourinho's team suffered an early blow when striker Fernando Torres limped off with a knee injury after 11 minutes and was replaced by Samuel Eto'o.
The substitute was involved in the opening goal nine minutes later as dangerman Andre Schurrle skipped past Daniel Georgievski on the left wing and teed up Eto'o.
His shot was mis-hit but Ramires followed up to lift the ball over keeper Ciprian Tatarusanu from three metres.
Chelsea made it 2-0 a minute before the interval when Tatarusanu parried an effort from Eto'o but the ball hit the unlucky Georgievski and rebounded into the net for an own goal.
ROOF CLOSED
The roof of the National Arena was closed before the match following persistent rain in recent days, allowing the home fans to create an intimidating atmosphere for the Chelsea players.
The Londoners, however, effectively killed the contest in the 55th minute when Ramires provided a thumping finish after Schurrle had surged down the left for the umpteenth time before finding Oscar who set up his fellow Brazilian.
Frank Lampard completed the rout with a low shot into the corner from 18 metres after good work by substitute Willian on 90 minutes.
The closest Steaua went to scoring was in the 73rd minute when Petr Cech had to pull off a fine save to parry Nicolae Stanciu's effort.
The Chelsea keeper also did well when he tipped Cristian Tanase's accurate chip over the bar and hurt his back in the process as he fell back against the woodwork.
The victory was sweet revenge for the 2012 Champions League winners who lost 1-0 here earlier this year in the last 16 of the Europa League before going on to defeat Benfica in the final in Amsterdam in May.
"Schurrle was fundamental," said Mourinho. "We identified what we had to do to penetrate their defence and he was the man for that.
"We always had control of the game. We scored four and probably could have scored six or seven because we played really well."
Steaua, the 1986 European champions, had boasted an admirable home record against English clubs with just one defeat in eight previous encounters.
The Romanians are back in the group stages for the first time since 2008.