Hyperinsulinism, impaired glucose tolerance, and hypertriglyceridemia may be risk factors for atherosclerotic heart disease and have also been described in patients with vertigo, whose symptoms and findings responded to appropriate dietary therapy. We studied 100 patients in an otolaryngology practice to determine the role of these abnormalities in identifying patients suitable for dietary therapy and to assess the efficacy of dietary therapy in the treatment of vertigo in such selected patients. The determination of hyperinsulinism and hypertriglyceridemia were of value as supplements to the traditional glucose tolerance test in detecting reversible metabolic vertigo. Reactive hypoglycemia was found in only four patients and thus appears overdiagnosed as a cause of vertigo. Insulin resistance appears to be the basic abnormality in this syndrome, which, in our series, occurred predominantly in overweight patients.