Twenty subjects with burning mouth syndrome (BMS) and 20 control subjects were tested for oral size perception. Blindfolded subjects assessed the size of holes (2.38-12.70 mm diameter) presented to the tongue, using their fingers to select a matching hole from a comparator series of 31 holes (0.76-15.87 mm diameter) using first static then phasic touch. Both groups overestimated the size of the holes less than 10 mm in diameter but no systematic disparity was evident with holes greater than 10 mm in diameter. The relationship between the stimulus size and the illusion (expressed as the ratio of apparent size to real size) was hyperbolic, with the illusion tending towards unity for holes greater than 10 mm. No differences were found in object size perception amongst patients with BMS or control subjects. It is therefore unlikely that altered oral size perception is a precipitating factor or accompanying feature in patients with BMS.