This report describes two patients with diabetes mellitus, presenting with insulin resistance and depression of erythrocyte insulin receptor binding to less than one-third of normal. Scatchard analysis of the data was consistent with a depletion in insulin receptors in these poorly controlled diabetic patients. Therapy with tolbutamide and reduced insulin administration resulted in restoration of erythrocyte receptor binding, clinical resolution of the insulin resistance, and amelioration of hyperglycemia. These data suggest a role for transient depletion and/or dysfunction of cellular receptors of insulin activity in the evolution of insulin resistance in diabetes.