A 29 was taken to hospital with serious head injuries after being assaulted outside a nightclub in Rochdale in the early hours of Saturday morning.
The incident happened outside The Empire Nightclub on Packer Street.
The victim remains there for treatment and his condition is described as serious but not believed to be life threatening at this time.
A 26-year-old man has been arrested on suspicion of assault and remains in custody for questioning.
Detectives believe that there may have been a number of witnesses to the incident, as well as a number of people who assisted the victims after he had been assaulted.
Police are urging those people to get in touch as a matter of urgency.
