Two men were attacked with broken paving slabs after challenging youths who were throwing stones.
The men, aged 27 and 32, challenged a group of teenagers who were throwing stones at a house in Falcon Brae, Livingston, West Lothian.
Police are hunting the group, who then attacked the men with pieces of broken paving slabs.
The 27-year-old sustained head injuries and was taken to the town's St John's Hospital.
The 32-year-old suffered minor injuries to his forearm but did not need medical treatment.
Police are appealing for information about the incident, which happened on Monday April 10.
Pc John McLean said: "This behaviour is absolutely unacceptable and we're appealing for the public's help as part of our ongoing investigation.
"Anyone who may have seen the group in the area, recognises the descriptions of the two males, or has any information about this is urged to get in touch."
Officers are keen to trace two youths in particular.
The first is described as being aged 15-17, 5ft 10in, of slim build, with short light-coloured hair. He was wearing a grey hooded top and grey jogging bottoms at the time.
The second is the same age, 5ft 8in, of slim build, with short light brown hair, and he was wearing a blue Diadora top and grey jogging bottoms.
Anyone with information can contact Police Scotland on 101 or Crimestoppers anonymously on 0800 555 111.
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