A MAN is fighting for his life after allegedly attacking another driver's car in Melbourne's east.

The 42-year-old man from Bayswater allegedly jumped on the bonnet of a Mitsubishi before falling and being caught under the wheel, as the other driver tried to pull away.

Police said the critically injured man was driving a Holden Commodore along Hull Rd in Lilydale at 1pm today, when the Mitsubishi pulled out in front of his car.

The man allegedly overtook the vehicle, stopped in the middle of the road and jumped on to the bonnet of the other moving car.

The 52-year-old man driving the white Mitsubishi was slowing down when his attacker jumped on the bonnet lost his balance and fell over the side becoming trapped under the passenger wheel.

He sustained critical injuries and has been taken to the Royal Melbourne Hospital.

The Mitsubishi driver from Western Australia is helping Police with their inquiries.