Alexis Sanchez nets 42nd minute free-kick to open the scoring.
Alvaro Negredo equalises five minutes into the second half.
Mesut Ozil thumps Arsenal back in front.
Steve Agnew still seeking first Premier League win at Middlesbrough boss.
Boro winless in the top flight in 2017 and six points from safety.
Arsenal now seven points adrift of the Champions League places.
Gunners secure first win at the Riverside Stadium since 2005.
Well that is about all we have time for from this night of Premier League action. We're back later this week with all the games from both the Champions League and Europa League where Leicester City and Manchester United are involved. But until then, goodbye.
That win sees Arsenal jumped into sixth in the Premier League and go with seven points of fourth place Manchester City, with a game in hand. Middlesbrough as six points from safety, second from bottom, with six games to play. A huge take for both sides to achieve their pre-season goals, you feel.
Full time: Middlesbrough 1-2 Arsenal
Not the most swashbuckling Arsenal win but a run of five on the road without three points is ended at Middlesbrough. Alexis Sanchez and Mesut Ozil are the heroes of the night. The home side put up stern resistance and did level through Alvaro Negredo but missed chances in the second half really cost them. Steve Agnew still without a top flight win as a manager.
Hector Bellerin - much maligned last week at Selhurst Park - and Francis Coquelin on to shore up the Arsenal backline as we enter four additional minutes.
Middlesbrough might be the lowest scoring side in the Premier League but they haven't half had some chances to be at least level if not ahead in this game. The latest opportunity comes as Friend diverts a Downing free-kick across goal and Gibson turns it goalwards - only for Cech to get down low to keep it out.
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Mesut Ozil hammers Arsenal into the lead for a second time at the Riverside.
Daniel Ayala with another header - not as easy as the one be spurned earlier in the second half - which Cech easily gathers. Five minutes for Arsenal to grind out.
That is eleven goals in all competitions for Mesut Ozil this season - better than he ever managed with Real Madrid in a single season. Food for thought.
Meanwhile, the game has reached a bit of a lull with Arsenal trying to put their foot on the ball while Middlesbrough look very rushed and rattled by going behind for a second time.
GOAL! Middlesbrough 1-2 Arsenal (Mesut Ozil)
No sooner am I bemoaning the German than he pops up with what could be the winning goal. Aaron Ramsey chests down Sanchez's dinked cross and lays it on a plate for Ozil who hammers through Guzan at the near post. The two contract rebels are looking set to dig Arsenal out of a hole here.
Adama Traore on for Middlesbrough and he is already making things happen down that right hand side, turning inside two Arsenal players, storming into the box but stumbling before the away side can clear.
Now Arsenal's turn to hold their heads in shame as a chance comes and goes. Sanchez picks out the run of Ozil but the onrushing Guzan snuffs out the chance as the Germany poked towards goal. Must admit, though the ex-Real Madrid playmaker pulled out of the tackle with the Boro 'keeper there.
Alvaro Negredo celebrates putting Middlesbrough on level terms.
Alexis Sanchez curls Arsenal into a first half lead.
Middlesbrough should be ahead now as Arsenal threaten to come apart at the seems. Downing is the provider again and when Gibson plays the ball across goal, Ayala is denied by a fine stop on the line by Cech.
Arsenal are all over the place at the back and they almost go behind when Stewart Downing takes the ball on the half-volley, but it flies over the bar. Middlesbrough back in this game in a big way now.
GOAL! Middlesbrough 1-1 Arsenal (Alvaro Negredo)
Middlesbrough were first out for the second half and they restart the game like a house on fire. Stewart Downing is allow to run deep inside the Arsenal half and when his cross evades Koscielny, Negredo is on hand to poke beyond Cech.
Players out and we're back underway in at the Riverside. The Premier League's lowest scoring club need a second half turnaround to boost their survival bid.
Half time: Middlesbrough 0-1 Arsenal
Boro plunged into further disarray as Arsenal take a lead into half-time. It's been an even game but both teams are separated by a moment of brilliance by Alexis Sanches, whose free-kick three minutes before the break has the visitors ahead. Middlesbrough have huffed and puffed, like they have for much of the campaign - but they have created little to trouble the back three deployed by Arsene Wenger.
GOAL! Middlesbrough 0-1 Arsenal (Alexis Sanchez)
Curiously named as one of the PFA Player of the Year nominees last week,the Chilean justifies that billing with his 19th goal of the season. He curls a free-kick over the Middlesbrough wall and with goalkeeper Brad Guzan rooted to the spot the ball nettles in the roof of the net.
Adam Clayton and Granit Xhaka battle for the ball.
Hard game to very overly excited about, as I feared before kick-off I must admit. Middlesbrough are dogged but lack any creative presence, while Arsenal are frustratingly lacking in cutting edge despite the millions of pounds worth of talent on offer.
Best opening of the night for Arsenal. Oxlade-Chamberlain scampers round the back and his clipped cross is headed back by Giroud towards Ramsey whose volley into the ground is cleared from Guzan's goal. Attacks have been rare from the visitors however.
Ball in the net for Middlesbrough but celebrations are cut short as De Roon is beyond the last Arsenal defender as he nodded beyond Petr Cech. A warning for Arsenal though, who have been typically lacklustre during the opening minutes.
Aaron Ramsey chases down a loose ball in the opening minutes.
Fabio's evening is indeed over as the ex-Manchester United full-back is replaced by the returning George Friend.
Fabio da Silva has recently returned from a head injury and has worryingly gone down clutching his head. The challenge with Oxlade-Chamberlain looked pretty innocuous, so perhaps there is some further damage. The Brazilian is on his feet but not sure yet whether he will be able to continue.
Boro have begun well here, pinning Arsenal back. Fabio drifts inside Oxlade-Chamberlain, who is hamstrung by his early booking and an exchange of passes almost sets up Negredo but the visitors clear.
Leadbitter actually picked up a hamstring strain in fouling Ozil a moment ago and has only just resumed. We'll keep an eye on his movement. Middlesbrough have made an otherwise encouraging start to the game.
Grant Leadbitter becomes the second player booked inside seven minutes, as he slides into Mesut Ozil. Let's hope that is the end of the bout of ill-discipline, or it might be an early night for one of two players.
Alex Oxlade-Chamberlain takes less than four minutes to get himself in the book, yellow carded for a late challenge on Fabio. Leadbitter takes aim from the resulting free-kick, shooting wide of Cech's goal.
Underway on Teeside. Must win for Middlesbrough and Arsenal. Should ensure a decent evening of entertainment. Should.
Players on their way out at the Riverside. The heavens have very much opened on Teeside, but can that add the necessary slickness to assist in producing an entertaining affair? Kick-off on the way.
Arsenal produced one of their worst performances under Arsene Wenger [how many times have we said that this season?] last Monday night against Crystal Palace, and they need a reaction tonight against another relegation threatened side. Middlesbrough are going to go direct but won't provide the same sort of threat in behind. Can the Gunners cope?
Steve Agnew on Sky Sports: "We have to try and expose any kind of weaknesses. We have to be well organised and threat when we get the opportunity. Arsenal have got some terrific players so we'll have to be at our best."
Chances are running out for Middlesbrough. A game in hand they may have but tonight is a must win surely.
Arsene Wenger playing three at the back tonight is a huge message sent to the Arsenal board. The Frenchman has been accused of being dated and failing to move with the times, but tonight he has proven he has the ability to change his way. Granted, it might have come too late to save their top four aspirations, but heading into next season this could be an important step.
More here on Brighton's promotion to the Premier League, 20 years on from the club almost dropping out of the football league.
Middlesbrough have made five changes from the draw with Burnley. Guzan, Barragan, Fabio, De Roon and Forshaw come in for the home side.
Arsenal made six changes and go to three to the back for the first time since 1997. Rob Holding makes his first start since August. Petr Cech and Laurent Koscielny return from injury.
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The Premier League has not been kind to Steve Agnew so far, with the interim Middlesbrough manager winless in his four games in charge which have yielded just two points and three goals. Can the visit of out-of-sorts Arsenal change things?
Teams should be with us at the top of the hour but until then let's look at how both teams might line up.
Middlesbrough welcome back George Friend from a calf injury and Gaston Ramirez following an ankle knock. Calum Chambers is ineligible to face his parent club.
Arsenal have Laurent Koscielny back after an ankle problem of his own. Petr Cech is also in contention but there is no place for Lucas Perez or David Ospina.
As the 2016-17 Premier League campaign enters the final stretch, points at this stage of the campaign are almost worth double and none more so than at the Riverside Stadium tonight. Middlesbrough are in desperate trouble - six points from safety - and despite having a handful of games in hand Steve Agnew badly needs to get his first top flight win on the board.
Arsenal are in similar turmoil. After five of the top six registered wins they reside in seventh, 10 points off fourth and a place in next season's Champions League. Arsene Wenger's future remains unresolved meanwhile, while Mesut Ozil and Alexis Sanchez are slipping closer to the exit door. Just who are the club in crisis again?
All the team news and build-up ahead of the 8pm kick-off on the way.
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