Arterial blood gases were analyzed in 121 patients with dizziness. Sixty-one showed arterial blood gas abnormalities in the dizziness period. An increase in bicarbonate was seen in 57, increases in both bicarbonate and arterial carbon dioxide pressure in 8, and a low arterial oxygen pressure in 22 patients. The frequency of the abnormalities was significantly higher in those with central-peripheral diseases than in those with Meniere's disease. Arterial blood gases were also checked at random in the remission period in 22 patients. The frequency of dizziness recurrence was significantly higher in patients with the abnormalities in the remission period than in patients without them. These results indicate that approximately half of the patients with dizziness tend to have arterial blood gas abnormalities in the dizziness period. It is suggested that arterial blood gas abnormalities cause temporary vestibular dehabituation that increases the frequency of dizziness in central-peripheral diseases and Meniere's disease.