Match ends, Brighton and Hove Albion 0, Middlesbrough 3.
Middlesbrough confirmed they will be top of the Championship at Christmas by winning at Brighton and ending the Seagulls' unbeaten start to the season.
Chris Hughton's side had avoided defeat in their opening 21 league games.
Kike's first goal since 18 August, a near-post header from Albert Adomah's fourth-minute cross, put Boro in front.
Adomah diverted in Daniel Ayala's header to make it 2-0 at half-time and Cristhian Stuani nodded in from close range after the break to seal victory.
Leaders Middlesbrough are three points clear of Brighton, who surrendered second place in the table as Derby won at Ipswich.
The home side's failure to deal with crosses proved to be their undoing, with all three of Middlesbrough's goals coming from centres into the box.
Brighton struggled to break through a resolute Boro defence, which kept their 12th clean sheet in 22 league outings this term and has not conceded a goal in any of their last six Championship matches.
The pundit's view
Former West Bromwich Albion striker Jason Roberts on BBC Radio 5 live: "Brighton could have been a bit more decisive. Make no mistake, they've come up against a really strong, well-oiled unit.
"(Middlesbrough head coach) Aitor Karanka hasn't shouted and screamed, he's been calm throughout and you can be when you've got a team that's only conceded 12 goals in the league.
"When you're coming up a side like that and you concede goals the way they have, it's very disappointing.
"Chris Hughton will be disappointed with the way they've gone about this game, but they need to maintain their focus because this is a team that could come very close to promotion."
A special visitor
News of Guus Hiddink's appointment as Chelsea manager broke during Middlesbrough's victory at Brighton, which was watched by his predecessor at Stamford Bridge - Jose Mourinho.
An agency representing the 52-year-old released a statement earlier on Saturday, which read: "He (Jose) will not be attending any high-profile games because he wants to discourage any speculation about his future."
But Mourinho did take in some Championship action later in the day and he watched Karanka - who was on Mourinho's coaching staff at Real Madrid - lead his side to an emphatic success.
What the managers said
Brighton manager Chris Hughton:
"Middlesbrough got an early goal and an early lift. We've now conceded four goals from corners in our last three games and that is something that needs to be eradicated.
"But we were up against a very good side and it's very difficult to be too harsh on the players.
"The reaction from our supporters at the end was excellent, and I hope the impact is positive and this defeat is a little bit of a reality check that allows us to get back to winning ways."
Middlesbrough head coach Aitor Karanka:
"Jose brought us luck. We worked together at Real Madrid and it was an amazing experience.
"He is a friend of mine. I didn't tell the players that he would be watching but it wasn't a secret.
"Afterwards, he came into the dressing room to offer congratulations. He felt he had watched a really good team and he was impressed with us. He was the best and he will be the best."
- 4HünemeierSubstituted forGoldsonat 60'minutes
- 27van La Parra
- 15MurphySubstituted forCroftsat 74'minutes
- 10HemedSubstituted forZamoraat 74'minutes
- 24NsueSubstituted forKalasat 74'minutes
- 8ClaytonSubstituted forZuculiniat 84'minutes
- 7LeadbitterBooked at 14mins
- 9KikeSubstituted forFabbriniat 65'minutes
- 10De Pena
- Craig Pawson
- Shots on Target
Second Half ends, Brighton and Hove Albion 0, Middlesbrough 3.
Attempt saved. Cristhian Stuani (Middlesbrough) right footed shot from outside the box is saved in the top right corner. Assisted by George Friend.
Offside, Middlesbrough. George Friend tries a through ball, but Albert Adomah is caught offside.
Attempt blocked. Dale Stephens (Brighton and Hove Albion) right footed shot from outside the box is blocked. Assisted by Bruno.
Attempt blocked. Íñigo Calderón (Brighton and Hove Albion) right footed shot from outside the box is blocked. Assisted by Dale Stephens.
Offside, Middlesbrough. Stewart Downing tries a through ball, but Diego Fabbrini is caught offside.
Foul by Bruno (Brighton and Hove Albion).
Diego Fabbrini (Middlesbrough) wins a free kick in the defensive half.
Foul by Íñigo Calderón (Brighton and Hove Albion).
Diego Fabbrini (Middlesbrough) wins a free kick on the right wing.
Substitution, Middlesbrough. Bruno Zuculini replaces Adam Clayton.
Foul by Bobby Zamora (Brighton and Hove Albion).
Tomas Kalas (Middlesbrough) wins a free kick in the defensive half.
Rajiv van La Parra (Brighton and Hove Albion) wins a free kick on the right wing.
Foul by Albert Adomah (Middlesbrough).
Attempt blocked. Bobby Zamora (Brighton and Hove Albion) header from the centre of the box is blocked. Assisted by Bruno with a cross.
Substitution, Brighton and Hove Albion. Andrew Crofts replaces Jamie Murphy.
Substitution, Brighton and Hove Albion. Bobby Zamora replaces Tomer Hemed.
Substitution, Middlesbrough. Tomas Kalas replaces Nsue.