One man is dead and another in Hawke's Bay Hospital's intensive care unit following a crash near Ruakituri Valley north of Wairoa.
Wairoa Police Sergeant Aubrey Ormond said the two 73-year-olds were part of a fundraising four-wheel drive rally being held on Nerana Station - a remote farm property south of Gisborne - when their vehicle went out of control and rolled down a steep 25m bank.
The vehicle ended up in a creek.
The pair were taking part in the annual three-day Mahia Hunt Four-Wheel Drive rally on Friday afternoon.
Mr Ormond said other drivers and passengers taking part came upon the crash scene and performed first aid on the men, while others called emergency services.
The remoteness of the area, which is about an hour by road from Wairoa, ruled out getting an ambulance to the scene.
Rescue helicopters from Gisborne and Hawke's Bay responded to the call and the two men were winched from the scene and transported to Hawke's Bay Hospital.
"Unfortunately one of the men died before reaching hospital," Mr Ormond said.
The deceased was the passenger in the vehicle.
The driver, from Cambridge, was admitted to the intensive care unit at the hospital where he was reported to be in a stable condition.
Mr Ormond said this morning the dead man's name had not yet been released as they were having difficulty finding and notifying next-of-kin.
He hoped to have the name released later today.
There had also been some uncertainty as to where he was from because he had several addresses on him - a place of work and two possible places of residence.
"It was an organised tour ... we are having a talk to everyone who witnessed the crash who was on the trek to find out exactly what happened," Mr Ormond said.
About 200 drivers, co-drivers and support crew had been taking part. The rallies have been running since 2005.
The accident takes the 2012 road toll for Hawke's Bay to six.