Fernando Torres scored twice as Chelsea hammered Genk to equal their biggest Champions League win.
Raul Meireles set the hosts on their way with a long-range effort before Torres took Frank Lampard's ball to notch the second with a cool finish.
Torres's angled header gave Chelsea their third, with Branislav Ivanovic heading in Florent Malouda's free-kick to put the Blues 4-0 up at half-time.
Substitute Salomon Kalou's second-half tap-in completed the rout.
The ease with which Chelsea strolled to victory bodes well for their trip to Belgium in early November, when a win will all but secure progression from Group E.
But more pleasing for the Blues will be the performance of Torres, who showed some of the ability that led to Chelsea paying Liverpool £50m for his services.
The striker, currently serving a three-match domestic ban and one of six changes from the Chelsea side that beat Everton on Saturday, may have thought he was in for another frustrating night in a blue shirt after poking an effort against the post when released by a delightful chip by Meireles.
But after Meireles - who was equally as influential as the Spaniard - took advantage of being unchallenged in a central position to fire a low long-range effort past Laszlo Koteles in the Genk goal, Torres took centre stage.
Fed by Lampard, another beneficiary of space in midfield, Torres moved through a gap in the Genk defence and finished past the on-rushing Koteles for his first Champions League goal since scoring against Chelsea for Liverpool in 2009.
Energised by that strike, Torres laid on a wasted chance for Malouda and shot over from a tight angle, then got a second that effectively killed the game as a contest midway through the first half.
Meireles was again involved, running down the right to meet Nicolas Anelka's pass, then whipping in a cross which Torres, who darted across the Genk defence, headed low into the far corner.
The Belgian visitors were offering little, bar three threatening balls from winger Kevin De Bruyn - a self-proclaimed Chelsea target whose mother was born in Ealing - all of which came to nothing.
Those moments on the back foot were few and far between for Chelsea, and they rounded off the first half with a deserved fourth goal when Ivanovic nodded into the bottom corner after climbing highest to meet Malouda's floated free-kick from the right.
With the hosts out of sight, the second half was little more than a procession as Meireles, Kalou and Jose Bosingwa all tried their luck from distance and Malouda had an effort beaten away when he perhaps should have squared for the unmarked Anelka.
But Chelsea did get the goal that sealed their biggest Champions League success since the 5-0 win over Galatasaray in 1999 when Bosingwa's whipped cross was met by Torres.
The Spain international was denied a hat-trick by Koteles' block, but the Genk keeper was powerless to prevent Kalou from the simplest of finishes.