Cardinia Highway Patrol officers are appealing for dashcam footage as they investigate a collision in Pakenham on Sunday night.
It is understood a black dirt bike collided with a black Mercedes SUV on McGregor Road at about 6.20pm.
The male rider was airlifted to hospital with life-threatening injuries.
The driver of the car stopped at the scene and spoke to police.
Anyone who witnessed the incident, has dashcam/CCTV footage or information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report at crimestoppersvic.com.au
