A 41-year-old man has been arrested on suspicion of attempted murder in connection with an assault in Bangor.
The Police Service of Northern Ireland (PSNI) said they responded to reports of a serious assault on Fort Road at 22:55 BST on Friday.
A man in his 40s was found lying unconscious on the road with a significant head injury.
He was taken to hospital where he remains in a serious condition.
A 41-year-old man was arrested at a nearby property on suspicion of attempted murder and other offences.
He remains in custody.
Police have appealed for anyone who was in the area at the time to contact them.