A 30-year-old man was sent to hospital on Friday after being assaulted in Bathgate.
The incident happened on Livery Street at around 11.30pm, Police Scotland said.
The victim was then taken to the Royal Infirmary of Edinburgh for treatment.
Officers are looking to trace a man described in his 20s, around 5’10” to 6’ in height, of medium build, with dark brown hair styled like a skin fade and clean-shaven.
He was wearing a grey t-shirt, possibly dark jeans, tattoo on his forearm.
Police said he was driving a red Mercedes.
Detective Sergeant John Bowerbank of CID said: “There were several people in the area at the time, and we would like to speak with them as they may have information that could assist our investigation.
“Anyone who can assist should call Police Scotland on 101 or speak to any officer quoting 5863 of June 16.
“Alternatively, information can be passed anonymously via the charity Crimestoppers on 0800 555 111.”