The brutal attack happened in Newtownards last night, Saturday, December 29.
Detective Constable Clare Killen said: “At around 10.20pm we received a report that a man in his thirties had been attacked by two unknown males as he was standing on Regent Street in the town.
“The pair kicked and punched the victim, inflicting a serious head injury for which he is now receiving hospital treatment.
“We are keen to hear from witnesses to the assault. We would also like to speak to anyone who may have seen any suspicious people or vehicles in the Regent Street, Lodge Lane or West Street areas before or after the incident.
“Detectives can be contacted at Bangor Police Station by calling 101, quoting reference 1293 30/12/17.”
“Alternatively, information can also be provided to the independent charity Crimestoppers on 0800 555 111 which is 100% anonymous and gives people the power to speak up and stop crime.