Gloucester were made to pay for their indiscipline as Amiln Challenge Cup holders Biarritz reached the last four.
A Mike Tindall try put the home side ahead but the French side scored 24 points while Dario Chistolini and then Koree Britton were in the sin-bin.
Dimitri Yachvili converted three tries while Damien Traille dropped a goal to put Biarritz 27-14 ahead at half-time.
Benoit Baby and Seremaia Burotu stretched the lead before Shane Monahan and Huia Edmonds' consolation scores.
VIEW FROM THE DRESSING ROOM
Gloucester director of rugby Nigel Davies told BBC Radio Gloucestershire:
"We weren't outclassed or outplayed, that's for sure. We weren't as good as we can be and we weren't as clinical as we should be.
"The two yellow cards (to Dario Chistolini and Koree Britton) had a huge significance on the game and there were a couple of other moments that had a big significance - that's the difference at this level.
"Two or three moments will win or lose you the game, we got them wrong and they got them right.
"This side is learning, it's learning how to win games, it's learning how to compete at the highest level and make no mistake, that Biarritz are one of the top teams in Europe."
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