The A308 Marlow Road has been closed at the Bisham Roundabout following a collision.
Officers from Thames Valley Police, fire crews and an air ambulance are at the scene.
Police are advising motorists to avoid the area.
Officers had received reports of a car colliding with a tree.
The car had gone off the road and a man was taken out of the car by 3.30pm.
Thames Valley Police said he was due to be taken to the John Radcliffe Hospital in Oxford but the extent of his injuries is unclear.
The car, a green Peugeot 106, was recovered shortly before 5pm.
Police cleared the road to be reopened at 5.05pm.
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