The efficacy of instant glucose as a potential treatment for hypoglycemia was studied in normal volunteers, with therapeutic doses administered in the buccal cavity. 2-Tritiated glucose (50 mu Ci) was homogenized into each dose before use. Mean blood glucose and serum insulin concentrations were unaltered by instant glucose. Glucose absorption was less than 0.05 mg at any time, and total glucose absorbed was less than 0.1 mg. For comparison purposes, volunteers swallowed a dose of instant glucose. Approximately 88% of the dose was absorbed during a 30-minute interval. Blood glucose and insulin levels increased. Instant glucose appears to be of therapeutic value only if swallowed by fully conscious, hypoglycemic patients. It should not benefit unconscious patients because of its poor absorption through the buccal mucosa.