A man suffered serious facial injuries after he was punched twice in Bedford Road, Northampton.
The victim was walking up Bedford Road towards Cheyne Walk between 11am and midday on Friday, when a man approached from behind and spoke to him.
As the victim turned to reply, the man punched him in the face, causing him to fall, when he was punched again.
The offender is described as white, about 5ft 9in, with a skinny build. He had dark shaved hair and a stubble beard.
Anyone with information can call Northamptonshire Police on 101. Alternatively, they can call the independent charity Crimestoppers anonymously on 0800 555 111 or use the anonymous online form at www.crimestoppers-uk.org.