It is a question of male Scottish dress that has formed the basis of curiosity and jokes for centuries.
But the delicate question of what a true Scotsman should, or should not, wear under his kilt may also have a contemporary political dimension, new research has suggested.
A survey of Scottish men has found that those who voted for independence in the 2014 referendum are significantly more likely to forego underwear when donning a kilt.
The research by YouGov found that 45 per cent of those who voted for independence state that they 'go commando', compared with 32 per cent who voted No.
Matthew Smith, a data journalist at the polling firm, said: "In Scotland, the notion of the 'True Scotsman' has long applied to one who does not wear anything beneath his kilt.