Ayr, Inverness and Paisley are expected to be in the running to become the first Scottish town to achieve such elevation since Dundee in 1889.
Ayr, site of the first meeting of the Scottish Parliament after the Battle of Bannockburn, has a strong claim. It has come a long way since Daniel Defoe described it as "like an old Beauty, shewing the ruins of a good Face ... from being the fifth town in Scotland, now like a Place forsaken".
Inverness, described by Dr Johnson as "capital of the Highlands", has been a royal burgh since the 12th century and contains the headquarters for most institutions dealing with the Highland region.
Paisley's claim is less obvious, given that it is seven miles west of Glasgow and includes Glasgow airport. It has shrunk in importance since the 19th century.
Only one town can win the competition and it will have to fight off competition from other parts of the United Kingdom. Candidates in England - Blackburn, Wolverhampton, Croydon, Stockport and Brighton - have shown their hand. But Scotland is seen as having a strong chance, because the 14 urban areas honoured this century have all been English or Welsh. The most recent were Armagh and St David's in 1994, in recognition of their long Christian traditions.
The Queen will choose the winner, to be announced next year, on the advice of the Government. The closing date for entries is 1 September. City status is granted by the Queen's personal command but the title carries no extra powers. The intention on this occasion is to celebrate the millennium and mark the 50th anniversary of her accession to the throne.