A 24-year-old had part of his ear bitten off when two men attacked him in a city centre.
The incident took place shortly after half-past midnight on Sunday March 30 near the junction of New Road and North Street.
The victim was taken to the Royal Sussex County Hospital, Brighton, for treatment to his left ear.
Detective Constable Christopher Hike said: "This was a nasty incident in which the victim sustained permanent injuries to his ear and had to undergo emergency surgery.
"We would like to speak to the man captured on CCTV who is holding a white phone in his hand and was wearing black jeans, a blue coat and light coloured shoes."
Anyone who saw what happened or who recognises the man on CCTV is asked to police on 101 or email firstname.lastname@example.org quoting serial 0057 of 30/03.
Alternatively, they can call the independent charity Crimestoppers free and without having to give their name on 0800 555 111.