A cyclist suffered serious head injuries when he crashed into a wall while being chased by a would-be robber in Preston, Lancashire Police said.
Two masked men riding a moped-style bike approached the 33-year-old victim at 20:25 GMT on Tuesday near Garstang Road's junction with Aqueduct Street.
When he tried to ride away he was chased by one attacker before being pushed into a wall.
One of the men searched him as he lay unconscious on the ground, police said.
It is not yet known whether anything was stolen.
They left on the moped towards Aqueduct Street.
The victim remains in a serious condition in hospital.
Police have urged anyone with dash-cam footage of the attack to come forward.