Full-time: Hull 32-24 Castleford
Castleford top of Super League
Hull FC current Challenge Cup holders
Live on BBC Two, Radio 5 live and local radio
Fetuli Talanoa
Talanoa gives Hull a second try
Hull work the ball out left to Fetuli Talanoa, who muscles off two tacklers and grounds the ball down.
Jake Connor is successful with a challenging conversion from close to the touchline.
What a fantastic start for the hosts.
Hull 6-0 Castleford
Fetuli Talanoa looks like he's got Hull FC's second try, but it will be reviewed...
Carlos Tuimavave
Hull's Carlos Tuimavave gets the first try
Castleford start a set of six inside the Hull FC half, and they have plenty of numbers over to the right.
Ben Roberts looks set to put Zak Haradker through a gap for the try, but Carlos Tuimavave intercepts his pass and races the ball back for Hull FC to open the scoring.
Jake Connor kicks the extra two points.
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Francesca Day: "Trip to the gym to do my injury rehab then home to watch the Challenge Cup on TV. Today is a great one for the neutrals."
Hull FC 0-0 Castleford
After a beautifully-observed minute's silence in memory of Hull FC legends Arthur Bunting and Dick Gemmell, and the victims of the London tower fire, the game gets under way.
Hull FC v Castleford (15:00 BST)
Image source, SWPIX.COMCastleford make two changes to the starting line-up which beat Warrington a week ago, with Jake Webster and Adam Milner in for Joel Monaghan and Grant Millington.
Forward Junior Moors, who was among the replacements against Warrington, misses out with a knee injury.
Castleford: Hardaker; Minikin, Webster, Shenton, Eden; Roberts, Gale; Lynch, McShane, Massey, Sene-Lefao, McMeeken, Milner.
Replacements: Millington, Patrick, Larroyer, Foster.
Hull FC v Castleford (15:00 BST)
Image source, SWPIX.COMHull FC make three changes from the side which beat Salford eight days ago, as forwards Scott Taylor, Mark Minichiello and Danny Houghton return.
Josh Bowden, Jansin Turgut and Jordan Thompson are named among the replacements after starting against the Red Devils.
Hull FC: Shaul; Michaels, Fonua, Tuimavave, Talanoa; Kelly, Connor; Taylor, Houghton, Watts, Washbrook, Minchiello, Manu.
Replacements: Bowden, Thompson, Fash, Turgut.
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Hull FC v Castleford (15:00 BST)
Image source, SWPIX.COMIf Hull are to defend the Challenge Cup, they may never face a bigger test than the one posed by today's opponents.
Castleford are the dominant force in Super League this season, having scored 149 more points than any other side, while also maintaining the stingiest defensive record.
But head coach Daryl Powell isn't expecting an easy afternoon at the KCOM Stadium.
"We need to play well, right at the top of our game, and give ourselves a chance," he told BBC Radio Leeds.
"If we're at our best and they're at their best it'll be an outstanding game, and probably as close to a 50-50 game as you could ever call."
Hull FC v Castleford (15:00 BST)
Image source, Getty ImagesHull FC had quite the season last year, reaching the Super League semi-finals and beating Warrington to lift the Challenge Cup at Wembley.
Lee Radford's side have continued to impress this season, sitting fourth in Super League, and still on course to defend their Cup title.
"There was some unbelievable feelings with that cup run last season, memories that the majority of the squad participated in," Radford told BBC Radio Humberside
"They know the ecstasy that comes with winning that cup, and it'll mean an awful lot to them on Sunday."
Hull FC v Castleford (15:00 BST)
If you aren't able to watch BBC Two's coverage of today's game, or just fancy a familiar voice to follow the action with, the BBC's local radio stations are on hand.
You can choose between BBC Radio Leeds and BBC Radio Humberside coverage by clicking on the links at the top of this page.
Image source, SWPIX.COMSalford reached the Challenge Cup semi-finals for the first time since 1998 with a 30-6 victory over Wakefield on Thursday.
Tries from Ryan Lannon, Ben Murdoch-Masila, Niall Evalds, Greg Johnson and Craig Kopczak booked their place in the next round, with Liam Finn getting Wakefield's only try.
On Friday, the Red Devils were joined in the last four by Leeds, who scored 10 tries in their 58-0 demolition of Championship side Featherstone.
Saturday: Warrington 26-27 Wigan
Image source, SWPIX.COMI'm expecting fireworks today between Hull FC and Castleford, but they'll have to produce something truly special to better the finish we saw between Warrington and Wigan yesterday.
Wolves twice fought back from 12 and eight points behind to level, before John Bateman's try and Sam Tomkins' drop-goal looked to have sealed it for the Warriors.
Kurt Gidley's try brought the hosts back within a point, before Stefan Ratchford's missed penalty from the halfway line left them with one last chance to force extra time....
Patton's last second drop-kick sails wide
If you want to watch full highlights of that game - and I really think you do - just click here.
Hull FC v Castleford (15:00 BST)
BBC Radio 5 live
Not only do we have BBC TV and local radio coverage for you to choose from, but BBC Radio 5 live are also in attendance at Hull.
Their commentary is just about to get under way, and you can listen in using the tabs at the top of this page.
Hull FC v Castleford (15:00 BST)
BBC Two
If you want to watch today's game, you can do so by scrolling to the top of this page and clicking the tab to watch BBC Two coverage.
Make sure you stick around after the match is over, as we'll also bring you the draw for the semi-finals and further discussion on the Rugby League Forum.
Hull FC v Castleford (15:00 BST)
Image source, Getty ImagesThey do say leave the best until last...
It's the fourth Challenge Cup quarter-final, and it should be a cracker.
Defending champions Hull FC play host to Super League leaders Castleford, for a chance to join Wigan, Salford and Leeds in the final four.