Police say a man sadly died at the scene early this morning.
The fatal crash near Bletchingdon happened just after 1am (20/02) and involved a silver DAF lorry and a pedestrian.
Formal identification has not yet taken place. Thames Valley Police said the man's next of kin were in the process of being informed.
Investigating officer, PC Alan Turnbull of the Serious Collision Investigation Unit based at Bicester, said: "I would appeal to anyone who witnessed the collision itself, or saw a pedestrian near, or on the A34 at Bletchingdon prior to the collision to contact police.
"We are also appealing to the driver of a dark-coloured Audi vehicle, who stopped at the scene following the collision, to come forward as we believe they might have information that can aid our investigation.
"If you have any information about the incident please call the 24-hour Thames Valley Police enquiry centre on 101 and quote reference number 77 (20/2).
"If you do not want to speak directly to the police you can contact the independent charity Crimestoppers anonymously on 0800 555 111. No personal details are taken, information is not traced or recorded and you will not go to court."