A sloppy second-half performance saw Bath slip to a frustrating 12-11 defeat to Biarritz in their Heineken Cup opener at the Rec.
The hosts made the brighter start and took an 8-0 lead into half-time after scrum-half Michael Claassens ran in the only try of the match.
But last season's runners-up hit back after the interval with Dimitri Yachvili kicking four penalties as Bath's indiscipline cost them dear.
Bath still had the chance to salvage a win in the closing stages but foolishly decided to go for the try-line rather than attempt a simple drop-goal from in front of the posts and Biarritz were able to hang on.
The hosts were on the front foot immediately at the start, collecting their own kick-off and earning a penalty after a high tackle from Australian centre Michael Bond.
Olly Barkley pulled his attempt wide of the near post but gave his side the lead shortly afterwards as he slotted a penalty through the posts after Biarritz were offside at a ruck.
With six minutes on the clock, Bath shipped the ball out wide to wing Matt Carraro, who cut inside and offloaded to Claassens for the opening try.
Barkley missed a difficult conversion to leave the lead at only eight points and shortly afterwards Biarritz finally started to apply some pressure, although handling errors and penalties cost them close to the try-line.
A score seemed inevitable when Bond picked up a loose ball and raced clear towards the line before playing in pacey American Takudzwa Ngwenya, but Nick Abendanon tracked back to make a fine try-saving tackle.
Errors continued to plague the Basque outfit as Bath maintained the 8-0 lead through an evenly-matched period as the half-hour mark passed.
There was a lull in the action as half-time approached when Biarritz's influential forward Imanol Harinordoquy received treatment, but the France international eventually got to his feet and was soon catching balls in the line-out.
Two minutes after the interval, the visitors got their first points on the board as Yachvili slotted over a kick after Bath were penalised in the line-out.
Barkley's inconsistent day with the boot continued as he missed a long-range penalty and Yachvili then added another three points to reduce the deficit to two.
Biarritz had a try ruled out by the video referee for a double movement, but reaped the rewards for their pressure as Yachvili slotted over another penalty to move them into a 9-8 lead in the 54th minute.
But Bath regained the advantage when Barkley nailed a penalty from just inside the Biarritz half after the visitors had collapsed a scrum.
The tables turned again 10 minutes from the end as Bath prop Davie Wilson was yellow carded for deliberate hands in the ruck and Yachvili once again slotted over the penalty.
Despite the numerical disadvantage, Bath surged deep into Biarritz territory but passed up a chance to retake the lead with a drop-goal and the visitors escaped and held on to win by the narrowest of margins.
Pens: Barkley 2
Pens: Yachvili 4
Bath: 15 Nick Abendanon, 14 Matt Carraro, 13 Shontayne Hape, 12 Olly Barkley, 11 Matt Banahan, 10 Sam Vesty, 9 Michael Claassens, 8 Luke Watson (c), 7 Simon Taylor, 6 Andy Beattie, 5 Danny Grewcock, 4 Stuart Hooper, 3 David Wilson, 2 Pieter Dixon, 1 Nathan Catt
Replacements: 16 Ross Batty, 17 David Flatman, 18 Duncan Bell, 19 Ignacio Fernandez-Lobbe, 20 Ben Skirving, 21 Mark McMillan, 22 Tom Biggs, 23 Jack Cuthber
Biarritz: 15 Dane Haylett-Petty, 14 Takudzwa Ngwenya, 13 Charles Gimenez, 12 Michael Bond, 11 Iain Balshaw, 10 Julien Peyrelongue, 9 Dimitri Yachvili, 8 Raphael Lakafia, 7 Imanol Harinordoquy, 6 Magnus Lund, 5 Erik Lund, 4 Manuel Carizza, 3 Campbell Johnstone, 2, Romain Terrain, 1 Eduard Coetzee
Replacements: 16 Benoit August, 17 Sylvain Marconnet, 18 Alexandre Barozzi, 19 Pelu Taele, 20 Benoit Guyot, 21 Damien Traille, 22 Arnaud Mignardi, 23 Ilikena Bolakoro
Referee: James Jones