A man has been arrested on suspicion of grievous bodily harm in county Antrim.
A 28-year-old man was assaulted on Castle Street in Ballycastle at around 2.30am this morning.
He sustained a serious head injury and remains in hospital.
A 32-year-old was arrested and is in custody helping police with their enquiries.
Anyone who was in the Castle Street area last night at around the same time as the incident is urged to contact the police.