An 82-year-old chased two burglars down the street after being attacked in his own home.
Joe Carter was hit repeatedly by two intruders in Guildford, Surrey, last Friday, and suffered serious injuries to his head and hands.
The burglars fled with nothing and the bloodied pensioner chased them down the street, before they escaped a getaway car.
A passing ambulance spotted him and he was taken to Frimley Park Hospital in Camberley, Surrey, where he is in a stable condition.
Detective Constable Dan Chant, from Surrey Police, said: "This was an horrific unprovoked attack on an elderly man and I am appealing for any information which might help locate these offenders.
"Anyone who may have been in the area and seen someone acting suspiciously or a vehicle being driven erratically is asked to call Surrey Police as soon as possible.
"I would like to take this opportunity to reassure the community that crimes of this nature are thankfully extremely rare."
Police are calling on witnesses to come forward with any information about the unprovoked attack, which took place between midday and 4.30pm on Friday, July 20.