The Barajas Airport in Madrid and the Welsh Assembly building in Cardiff are up against schemes by David Adjaye, Hopkins Architects, Caruso St John and Zaha Hadid.
The shortlist is:
the Welsh Assembly Building, by the Richard Rogers Partnership;
Barajas Airport in Madrid, by the Richard Rogers Partnership;
Whitechapel Idea Store, by Adjaye Associates;
The Evelina Children's Hospital, by Hopkins Architects;
The Phaeno Science Centre in Wolfsburg, by Zaha Hadid Architects; and
Brick House, by Caruso St John Architects.
This represents Zaha Hadid's second chance in two years for glory after she also made it into the last six last year with her BMW factory.
But the favourite is likely to be Barajas, which has been widely acclaimed in both the UK and Spain.
This year's dark horse is the Brick House by Caruso St John, which will be considered to have done well to get to this point.