Passers-by used a fire extinguisher to put out flames which took hold in the engine bay of the man's car, as firefighters worked to cut the trapped woman from her wrecked car.
It appeared the woman, in her 50s, who was driving on State Highway 6 towards Cromwell, had crossed the centre line on a curve about 50km from Queenstown, Sergeant Keith Newell,of Queenstown, said.
Her car hit the man's Subaru Outback, he said.
There were no passengers in either car.
The Subaru was pushed against a road barrier and stopped in a lay-by.
A passing nurse stopped to help the injured pair, who were treated by St John ambulance officers when they arrived.
Traffic was stopped to allow helicopters to land on the road.
Two helicopters had been sent to the scene, and the man and woman were transported to Dunedin separately. Both appeared to be conscious when placed in the helicopters.
A St John spokeswoman last night said the 30-year-old man had serious leg injuries while the woman had serious chest and abdominal injuries.
Sgt Newell said the drivers were not believed to be tourists.
Asked if charges would be laid, he said inquiries were continuing.
