A man was found lying unconscious in the street after he was attacked by a group of youths.
The 22-year-old victim, who has not been named, was discovered outside Southwick Community Centre in Southwick Street.
A member of staff at the nearby Pilot pub raised the alarm and called an ambulance.
The victim was taken to the Royal Sussex County Hospital, Brighton, but was allowed home after treatment.
Inspector Chris Drew of Shoreham police said: "The attack is believed to have been carried out by a number of youths but we have not been able to find anyone who saw it.
"We need to hear from anyone who witnessed the attack or who has information about those involved."
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