Two men had to be cut free from a car by firefighters early on Sunday morning after a crash in Sittingbourne Road, Maidstone.
The accident happened shortly before 7.30am at the junction with Hatherall Road and only one vehicle - a blue Rover - was involved.
Firefighters used hydraulic cutting equipment to release the occupants of the car. One was taken to hospital by land ambulance and the other by the Kent Air Ambulance.
Emergency services were at the scene for nearly 90 minutes and a section of the Sittingbourne Road closed. Kent Police say they expect to re-open it at midday.
The driver of the car, a 21-year-old man from Maidstone, was taken by ambulance to the Medway Maritime Hospital with a leg injury.
The passenger, a 22-year-old man from Maidstone, was flown by air ambulance to King's College Hospital, London, with a serious head injury.
PC Rob Malins of the Kent Police Serious Collision Investigation Unit said: “The Rover was travelling along the A249 Sittingbourne Road towards Maidstone town centre when, just before the junction with Hatherall Road, it has lost control, crossed over the road and collided with a wall outside a house at the end of Hatherall Road.
"We would like to hear from anyone who saw the collision or events leading up to it. Please call the Kent Police Serious Collision Investigation Unit appeal line on 01622 798538.”