Police are seeking witnesses to an incident in Shoreham-by-Sea earlier this month in which a 26-year-old woman was punched to the ground unconscious.
The spokesman said the incident in Middle Road happened around 8.45pm on April 19.
They said: "The victim had been involved in a brief verbal altercation with a man, who then struck a blow to her head. As a result of the assault, the victim sustained serious injuries and was taken to Worthing Hospital for medical treatment.
"Her suspected assailant is described as a white man in his early 20s, 5'10", of average build and with short dark hair, cropped at the sides and flat on top. He was wearing a blue t-shirt and jeans."
Detective Constable Lee Elliott said: "We're investigating the circumstances and are keen to speak to anyone who may have seen what happened or who has other information."
Details can be submitted online or by phoning 101, quoting serial 1431 of 19/04. Alternatively, please visit the Crimestoppers website or contact the independent charity anonymously on 0800 555 111.