Racing 92 ruthlessly saw off Harlequins with a bonus-point win that gives them a strong chance of qualifying for the Heineken Champions Cup quarter-finals.
A Teddy Thomas score three minutes in set the tone as the Top 14 outfit ran in seven tries at Twickenham Stoop.
The visitors were 35-0 up before Harlequins mustered a response through a Scott Steele try on the hour mark.
Racing have a maximum 10 points in Pool B but Harlequins remain winless and without a point after two games.
Clinical Racing too hot for hosts
After an opening defeat by Munster, Harlequins head coach Paul Gustard said his side must improve to get anything from a "formidable" Racing team.
They got off to the worst possible start against a side who have been beaten finalists twice in the past three years, as Thomas punched through a hole to race over after three minutes.
Marcus Smith hit the post with a long-range penalty as Harlequins looked to respond but Maxime Machenaud soon increased the visitors' lead with a penalty of his own, adding another later in the half.
Kevin le Guen burrowed over from the back of a maul to complete the first-half haul and immediately after the interval Simon Zebo finished on the left for his 32nd try in the competition.
With half an hour to go, the Parisians already had a bonus point.
Replacement Georges Henri Colombe crashed over and a delightful kick to the corner from fly-half Finn Russell allowed Donovan Taofifenua to also cross.
Steele scampered over for a consolation as Racing briefly switched off, only to re-establish their advantage through Teddy Baubigny following sustained pressure.
Francois Trinh-Duc made it seven tries for the visitors, and even a final flourish for Quins was chalked off after an infringement by Chris Ashton in the build-up to Alex Dombrandt's score.
Line-ups
Harlequins: Brown; Earle, Marchant, Tapuai, Murley; Smith, Care; Marler, Baldwin, Louw, Tizard, Young, Lawday, Evans, Dombrandt (capt).
Replacements: Elia, Els, Baxter, Lamb, J Chisholm, Steele, Lang, Ashton
Racing 92: Zebo; Thomas, Beale, Chavancy (capt.), Taofifenua; Russell, Machenaud; Ben Arous, Le Guen, Oz, Le Roux, Bird, Lauret, Chouzenoux, Sanconnie.
Replacements: Baubigny, Kolingar, Colombe, Ryan, Diallo, Le Garrec, Trinh-Duc, Imhoff.
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