Glucagon normally plays a primary role in promoting glucose recovery from insulin-induced hypoglycemia. Epinephrine compensates largely for deficient glucagon secretion. Glucose recovery from hypoglycemia fails to occur only in the absence of both glucagon and epinephrine. Perhaps as a relatively early feature of autonomic neuropathy, patients with insulin-dependent diabetes mellitus commonly have blunted or absent glucagon secretory responses to hypoglycemia. However, this deficient response is commonly compensated for by epinephrine and glucose recovery occurs. In some patients, progression of adrenergic neuropathy to the point of deficient epinephrine secretory responses to hypoglycemia, coupled with deficient glucagon responses, leads to frequent, severe, and prolonged hypoglycemia. Thus, these glucose counterregulatory systems are of critical importance to patients with insulin-dependent diabetes mellitus. The efficacy of glucose counterregulation in a given patient may determine the degree to which euglycemia can be achieved with aggressive insulin therapy in that patient.