A man was knocked unconscious and suffered serious facial injuries after being assaulted in a nightclub.
Police said the man was punched and knocked to the floor at Rock City in Nottingham city centre.
The assault took place in the cloakroom foyer of the venue on Talbot Street at about 02:45 GMT during the 'Tuned' student night on 3 November.
Nottinghamshire Police have urging people who may have seen the attack to come forward.
Det Con Nabeel Dad said: "This nasty assault took place in the cloakroom area and would have been seen by people in the club."
"We are looking to speak with anyone who witnessed the attack and who may have any information that could aid our investigation.
"We would urge you to come forward and get in contact as soon as possible."