The effect of epinephrine and isoproterenol in different concentrations and adrenergic blocking agents on glucose induced insulin secretion and glucose utilization was studied in isolated islets of Langerhans from mice. Epinephrine in physiological concentrations significantly inhibited the glucose induced insulin secretion. This effect was not mediated by a change in glucose utilization but involved alpha-adrenergic stimulation. Isoproterenol significantly stimulated the glucose induced insulin secretion but had no effect on glucose utilization. Beta-adrenergic stimulation by isoproterenol at low glucose concentration was not sufficient to stimulate insulin secretion. The results are discussed in relation to current therories on the mechanism of glucose induced insulin secretion.