Adelaide police say two men who assaulted another at a house at Parafield Gardens were looking for drugs.
They say a man had gone to the door of the house in Blackie Avenue when someone knocked late on Wednesday night.
Police say the attackers, in their 20s, were armed.
The victim is in the Royal Adelaide Hospital with injuries to his head and arms.
Neighbours said they heard screams.
“We heard this shuffling and yelling and screaming, you know, yelling of voices and then we actually saw the shadows of people running,” said a neighbour, Shirley.
Chief Inspector Tony Crameri says no drugs were found at the property and the man may be the victim of mistaken identity.