Edinburgh have one win and one loss so far
Castres beaten in both of their pool matches
HT: Castres 21-14 Edinburgh
John Barclay
Former Scotland captain on BT Sport
It's been a superb game.
Castres feel like they've got the bit between their teeth - they'll be looking forward to the second half.
Castres 21-14 Edinburgh
An entertaining half, but another showing where Edinburgh have shipped points with alarming ease.
Work to do for Mike Blair at the break.
Wilfrid Hounkpatin
Pure power results in the hosts' third try of the game.
Castres' big number three takes the ball, readies himself, and drives over from close range.
The conversion is good.
Castres 14-14 Edinburgh
Castres kick to the corner as we approach half-time.
Can Edinburgh keep them out?
Castres 14-14 Edinburgh
John Barclay
Former Scotland captain on BT Sport
It's been a good game so far. Both teams are looking to play.
Castres 14-14 Edinburgh
End-to-end stuff in the south of France.
Castres are the side on the front foot now.
Jack Blain and Cammy Hutchison do well to slow the ball down, but the hosts have a penalty advantage to fall back on.
Bill Mata
He's unstoppable from there!
Edinburgh go through the phases, and Bill Mata crashes over from close range.
The visitors did well to keep the ball alive in that passage of play and tire out Castres' big men.
Blair Kinghorn's conversion is good, and Edinburgh are level again.
Castres 14-7 Edinburgh
Some slick hands from Cammy Hutchison and Charlie Savala free Mark Bennett, who races into the Castres 22.
Big chance...
Adrien Seguret
Too easy.
Castres centre Adrien Seguret receives the ball off the back of the scrum, steps off his left foot, and dives over under the posts.
The conversion sails through - the hosts have turned this on its head.
Castres 7-7 Edinburgh
Edinburgh's lineout, which has been a weakness all season, wobbles again.
The ball back to Charlie Shiel goes straight to ground, and the scrum-half knocks-on, leaving Castres with a 5m scrum.
Sloppy.
Castres 7-7 Edinburgh
Edinburgh do superbly to halt the Castres maul, and then drive it into touch.
The capital outfit have a lineout deep in their own territory, and a chance to clear their lines.
Castres 7-7 Edinburgh
The hosts are turning the screw here.
A penalty is kicked to the corner, as they look to take the lead.
Castres 7-7 Edinburgh
Edinburgh's restart is rather heavy, and rolls out of play behind the Castres dead-ball line.
The hosts gifted a scrum on halfway.
Josaia Raisuqe
Castres hit back.
A delicate kick in behind from home fly-half Benjamin Urdapilleta picks out the onrushing Josaia Raisuqe, and the Fijian flanker dots down ahead of Henry Immelman.
Urdapilleta knocks over the conversion, and we're all square.
Castres 0-7 Edinburgh
Edinburgh's 11 cynically slows down the play to allow his teammates to recover in defence, and is duly shown a yellow card.
Edinburgh will have to play the next 10 minutes with 14 men.
Castres 0-7 Edinburgh
Some great hands take Castres to within inches of the Edinburgh line.
Can the visitors keep the French side out?
Dave Cherry
Over they go!
A powerful maul marches towards the line, before Dave Cherry breaks away and stretches out to score the game's first try.
Blair Kinghorn adds the extras.
Castres 0-0 Edinburgh
A scrum penalty goes the way of Edinburgh - great work from WP Nel.
Blair Kinghorn kicks to the corner, and Edinburgh will look to maul their way over...
Castres 0-0 Edinburgh
A nice little wrap-around creates an overlap for Edinburgh, but the final pass is in front of Jack Blain, and bobbles out into touch.
A good chance goes begging.
Castres 0-0 Edinburgh
Pierre Schoeman does superbly to get over the ball and steal possession for Edinburgh.
No real chances as of yet in this game.