Russian side Enisei-STM recorded the shock of the round as they defeated Aviva Premiership side Worcester Warriors 19-12.
Tries from Josh Adams and Derrick Appiah weren't enough for Worcester as Enisei-STM fly half Yury Kushnarev slotted three penalties and a conversion to earn his side an historic win.
Edinburgh got their Challenge Cup campaign off to a perfect start with a 59-17 win over Romanian side Timisoara Saracens.
Stuart McInally and Nasi Manu each bagged themselves a hat-trick, while Viliame Mata crossed for brace with Michael Allen rounding off the scoring.
Meanwhile in pool 1, La Rochelle blew away Italian outfit Benetton Treviso 41-10 notching up five tries in the process.
The Ospreys kicked off their European Challenge Cup campaign with a 45-0 defeat of Newcastle at the Liberty Stadium.
Newcastle have made an encouraging start to the Aviva Premiership season but they had no answer to the Welsh region, who ran in seven tries in all.
Fly-half Dan Biggar ended with 15 points, via a try and five conversions, while Rhys Webb, Ashley Beck, Scott Baldwin, Justin Tipuric and Keelan Giles (2) also scored.
Elsewhere in Pool 2, visitors Lyon also secured a bonus-point win as they secured a 39-13 win in their all-French clash at Grenoble.
Cameron Mapusua, Thibault Regard, Deon Fourie and Henry Clunies-Ross scored the visitors' tries while Jacques-Louis Potgieter added 19 points with his boot.
Grenoble opened the scoring thanks to Loick Jammes' converted try. Gilles Bosch kicked eight points for the hosts.
Newport Gwent Dragons, meanwhile, opened their Pool 3 campaign with a bonus-point 37-16 defeat of Brive at Rodney Parade.
Rynard Landman, Lewis Evans, Cory Hill, Hallam Amos and Adam Warren all touched down as the hosts scored five tries to Brive's one.
In Pool 4 Cardiff Blues continued a good night for Welsh clubs as they beat Bristol 33-20.
Reynold Lee-Lo, Josh Turnbull, Alex Cuthbert and Tom James scored tries as the Blues secured a bonus point. Gareth Anscombe added 13 points with his boot.
Max Crumpton and Joe Joyce scored for the hosts, who are yet to win this season.