Police are appealing for witnesses after a man died as a result of a collision on the A689 near Killhope shortly before 9pm on Monday.
The two vehicles involved were a quad bike and another vehicle.
The quad bike was believed to have been stolen from a farm in the Alston area.
A Durham Police spokesman said: “Sadly the man, who was in his 30s, was pronounced dead at the scene.
“Two men were arrested on suspicion of causing death by dangerous driving and have been released under investigation.”
Enquiries are ongoing but anyone with any information or dash cam footage which could help the investigation, should call Durham Constabulary on 101, quoting incident 447 of January 6.