Intravenous tolbutamide evoked an exaggerated hyperinsulinemia in persons with mild glucose intolerance, i.e. in those with equivocal Glucose Tolerance Sums or so-called chemical or latent diabetes. The tolbutamide-induced hyperinsulinemia was greater in those who were older and in those who were overweight. Such hyperinsulinemic responses in association with this limited degree of glucose intolerance were also present in the younger and older members of the non-overweight group. Such individuals with mild glucose intolerance and an exaggerated tolbutamide-induced hyperinsulinemia also developed greater increments in serum insulin following the ingestion of glucose. 1 Aided by grants from the Addison H. Gibson Foundation, John and Rosalind Redfern, the Pittsburgh Foundation (Charles A. Locke Educational and Charitable Trust), and the Commonwealth of Pennsylvania