Sunderland, Middlesbrough and Newcastle United fans have been urged to behave on one of the biggest weekends in the football calendar.
It's FA Cup third round weekend, and Newcastle United, Sunderland and Middlesbrough are all involved in the big games - the last two in a Tees-Wear derby.
It will be the second time this season that Sunderland and Middlesbrough have met on Teesside - Boro won the league clash at the Riverside 1-0 back in November.
Tomorrow's game, which has an earlier-than-usual 1pm kick-off, will see the Black Cats have the backing of a sold-out allocation of 4,400 away fans.
A crowd of around 30,000 is expected, and police today said they hoped both sets of fans will co-operate to make it a trouble-free occasion.
Superintendent Dave Sutherland said: “Cleveland Police works with Middlesbrough FC and others to ensure that football matches are as safe, crime-free and as enjoyable as possible.
“The vast majority of those attending the game will be genuine fans who turn up to support their team with family and friends.
"Both clubs have a passionate and vocal following and Middlesbrough should be proud of the huge support shown to them by their fans.
“There are, unfortunately, a minority of people who sometime use football as an excuse for causing trouble through antisocial, drunken or violent behaviour.
"At best this spoils it for genuine fans and at worst it can undermine public safety.
"Such behaviour will not be tolerated and we will work with the football clubs to ensure that those responsible for this type of behaviour are prosecuted and/or banned from future games.”
“Saturday is an opportunity for people to come to Middlesbrough for a great day out, and additional police officers will be on duty to ensure a safe and enjoyable day.”
On Tyneside, Northumbria Police are preparing for an even bigger crowd at St James's Park, where Newcastle United face Luton Town in a 3pm kick-off.
The League Two side's supporters are expected to travel in numbers from Bedfordshire, with 7,500 visiting supporters snapping up tickets for the match - one of the biggest away followings the city has seen in many years.
The police commander for the fixture said today that he is looking forward to a great atmosphere - and an FA Cup classic.
Chief Inspector Jamie Pitt said: "We are delighted to be involved in the policing of a good, old-fashioned 3pm FA Cup third round game, and are expecting an excellent atmosphere this weekend.
"Luton Town fans will be travelling in large numbers, so it is appropriate and proportionate for us to put a policing operation in place to minimise any disruption to the city.
"We will be working closely with the football club, the local authority and British Transport Police to make sure we can enjoy the atmosphere and tradition of the FA Cup third round weekend.
"However, if anyone does have any concerns, whether you are a visitor to the city or a football fan, then please do stop our officers and say hello."
Sunderland fans travelling to the game can get all the information they need about travel, turnstile times and away bars by following @NPSAFC on Twitter this weekend.
Fans from both Newcastle and Luton are also being encouraged to follow @NPNUFC on Twitter for updated information around this weekend's fixture.
Anyone who wants to report anything to police ahead of either of the matches, or on the day of the game itself, can do so by calling 101, or reporting it online at www.northumbria.police.uk/contact. In an emergency, or if a crime is in action, you should always contact 999.