A man was treated in hospital for a head injury sustained after he was attacked with a metal pole.
The assault happened in Nelson Street, Kettering, between when the victim was walking along the road, near the junction with Regent Street.
A police spokesman said the man was attacker by someone believed to have been carrying a metal pole.
The victim was taken to Kettering General Hospital for treatment.
Witnesses, or anyone with information, is asked to call Northamptonshire Police on 101. Alternatively, they can call the independent charity Crimestoppers anonymously on 0800 555 111.