BBC News, South East
Now in its 15th year, the race is due to start in Preston Park at 09:45 BST and end at Hove Lawns.
The Brighton & Hove 10K (6.2 miles) event is also being held.
Road closures start from 06:00, while Preston Park and London Road railway stations will be closed until 11:00, with marshals at the city's main station to direct runners to the start line.

Among those taking part will be Kristina Goodsell, from Married at First Sight, who is raising awareness of the condition premenstrual dysphoric disorder.