The frequency component of shift in the centre of gravity while standing upright was investigated in 14 normal subjects and 30 patients with peripheral vestibular disease. Relative changes in the square root value of the power in each small frequency band of 0.1 and 0.2 Hz in frequencies of less than 2 Hz were evaluated statistically for four groups, viz. a group of normal subjects, and patients with Ménière's disease, benign paroxysmal positional vertigo, and vestibular neuritis. The influence of visual control in each group and the difference between each pathological group and the normal subjects were examined statistically. The combination of a minor change in each small frequency band is considered to be utilizable to establish a differential diagnosis for the three groups of peripheral vestibular disease and versus the normal group.