Championship side Middlesbrough reached the Capital One Cup quarter-finals with a deserved win against Sunderland in the Wear-Tees derby.
Scott McDonald's neat finish close to half-time was enough for Boro to avenge last season's FA Cup fourth round exit by their Premier League rivals.
McDonald also hit the Sunderland bar, while Black Cats goalkeeper Keiren Westwood denied Faris Haroun.
Stephane Sessegnon went closest for the hosts after a powerful run and shot.
Australian striker McDonald's winner clinched a fifth straight win for in-form Middlesbrough, who had failed to beat Sunderland in the previous six meetings between the north-east rivals.
It proved an enjoyable return for Boro's former Black Cats players Justin Hoyte and, particularly, Grant Leadbitter - who grew up a Sunderland fan and spent seven years with the club before moving to Ipswich.
Former Boro player Lee Cattermole was given a cool reception by the away fans, while Adam Johnson was also unable to make an impression against the club where he too learned his trade.
Sunderland started brightly and Jason Steele was forced into an early save from England winger Johnson's inswinging corner.
However, Boro soon settled and enjoyed midfield dominance through the energetic Leadbitter and Nicky Bailey.
Faroun drilled wide from outside the box, before testing Westwood with another strike, and half chances for McDonald and Leadbitter further demonstrated their intent.
Mowbray's side looked particularly dangerous on the break and McDonald hit the bar with a curling shot from the edge of the box.
John O'Shea headed just wide for Sunderland from Johnson's cross, but Boro eventually took the lead their pressure deserved.
Ishmael Miller tricked his way into space down the right and his cross was turned in by McDonald at the near post.
O'Neill's side emerged after the break with renewed momentum and created two quickfire chances. First Louis Saha drifted over the bar from distance, before Fletcher skidded a shot into the palms of Steele.
The home support grew exasperated with the lack of penetration, as did O'Neill who withdrew Saha for winger James McClean.
For all their hard work, the Black Cats could find no way through an organised Boro defence and were fortunate to see a shot from Bailey drift harmlessly over the crossbar.
McDonald and Haroun continued to work Westwood, who proved equal to their long range shooting, while Sunderland brought on Fraizer Campbell for Johnson in their bid to take the game to extra time.
McClean fired a shot towards goal which was deflected for a corner and Sessegnon headed wide from the set-piece.
Four minutes of added time increased the tension, but Boro hung on to knock their rivals out as boos rang around the Stadium of Light at the final whistle.
Middlesbrough manager Tony Mowbray on BBC Tees:
"For the fans who travelled in such big numbers, it's great to send your supporters home happy. The fans are fantastic, my job is to give them nights like tonight.
"We worked on a game plan, the game plan worked well and we could have broken away and scored late on.
"The team are in confident mood, Scott [McDonald] is back with a smile on his face - he's so desperate to do well. I asked him to play wide today and he did so like a trojan."
Sunderland manager Martin O'Neill on BBC Newcastle:
"We didn't have enough clear-cut chances, and taking the wrong option at times didn't help either. It was a disappointing night.
"I think there are areas for major consideration, we didn't deal with the emotion of the occasion, didn't do well enough and we're supposed to be able to cope with the pressure when things don't go for us.
"We need to be big enough to deal with that pressure and we need to pick the option under adversity. In their minds the players should be able to pick the right choice - to play."