A blood-stained man who was found wandering in Kilmarnock town centre has no recollection of how he was injured, police have said.
CCTV operators alerted officers after spotting the man in the town's Grange Street at about 0210 BST on Monday.
He was treated in Crosshouse Hospital for multiple injuries and released the following day.
Police believe the man was seriously assaulted and have appealed for anyone with information to contact them.
Det Con Bob Reid, of Strathclyde Police, said: "I am very keen to speak to anyone, passers-by or in vehicles, who were in the Grange Street area of Kilmarnock in the early hours of Monday morning and may have seen this man or have any knowledge of how he came to be injured.
"I would also like to speak to anyone who knows why this serious assault happened or has any knowledge of the person or persons responsible."