A man was punched in his face in an early morning attack in Sheffield city centre.
The 18-year-old was attacked after being approached by a group of four men outside Yates's on Cambridge Street at 3.15am on Saturday.
Police officers investigating the incident said the men were in their early 20s and one was wearing a white T-shirt.
Those involved made their way towards Carver Street afterwards.
The victim needed hospital treatment following the attack.
Anyone with information should call South Yorkshire Police on 101.