The most northerly battle fought by imperial Rome could be left out of an inventory of Scottish battlefields due to uncertainty over the site.
Mons Graupius in AD 83 or 84 saw the 9th Hispana, its cohorts and Roman cavalry defeat 30,000 Caledonians.
Locations suggested in the past include Dunning in Perthshire, Carpow in Fife, Bennachie in Aberdeenshire and Culloden in the Highlands.
Historic Scotland said an accurate site was needed for inclusion on its list.
The body has commissioned research on Mons Graupius along with a number of other battle sites.
It has already placed several battlefields including Bannockburn in 1314 and Culloden in 1746 on Scotland's Inventory of Historic Battlefields and earlier this month put out 11 other sites for public consultation.
The list, which includes details on the boundaries and armies involved, will act as a guide to planning authorities.
Historic Scotland's Dr Lesley MacInnes, said a decision had still to be made on whether Mons Graupius should be put forward for consideration as an entry on the inventory.
The head of battlefields said: "We have recently commissioned the research for a number of battlefields including Mons Graupius.
"The research will review all available evidence for these sites to establish if they meet the published criteria for inclusion in the inventory.
"Early sites such as Mons Graupius present particular challenges for accurate location which is one of the required criteria for inclusion."
Dr MacInnes added: "Any sites which are considered to be of national importance but cannot be accurately located cannot be included at this stage but will be kept under review should further information emerge to allow their inclusion.
"The research outcome for Mons Graupius will be clarified by the end of the financial year."
Mons Graupius is believed to be wrapped up in the mysterious disappearance of the 9th Hispana in AD 120.
The legion, cohorts of auxiliary light infantrymen from Gaul and Batavia along with cavalry were heavily outnumbered by Caledonians at the battlefield.
However, the tactics of Roman general Gnaeus Julius Agricola left 10,000 tribesmen dead but relatively light casualties among the auxiliaries.
There has been a long running debate on where the battle was fought.
In his book Legions of Rome, historian Stephen Dando-Collins said no location has been "reliably fixed".
Potential sites have been weighed up on the website Roman Scotland.
It rates Dunning the most likely and Culloden among the least.
Sites close to the Grampian mountains have also been suggested in the past.
In his book, Dando-Collins connects Mons Graupius with the disappearance of the 9th after it was later posted to Carlisle.
He said Caledonians had sought revenge for the defeat and ambushed and slaughtered the legion along with its affiliated units.
Mystery surrounding the fate of the 9th inspired Rosemary Sutcliff's children's book Eagle of the Ninth and two recent films - The Eagle and Centurion.
Scenes for The Eagle starring Channing Tatum and Jamie Bell were shot around Achiltibuie and Old Dornie, near Ullapool, and in the Cairngorms for Centurion.