Three clinical cases of profound hypoglycemia are described with survival periods ranging from 2 1/2 months to 6 years. Although prolonged clinical coma was present in all cases, only subtle evidence of neuronal loss was found. The value of immunohistochemical examination of the grey and white matter of the telencephalon in detecting evidence of neuronal loss in such cases is demonstrated. Infarcts were uniformly absent, as would be expected from the lack of cerebral acidosis in hypoglycemia. In addition to the usual absence of infarction, the pathologic findings in hypoglycemia distinguish themselves from hypoxic/ischemic encephalopathy in that the cerebellum is regularly spared, and that there is sometimes a characteristic involvement of the dentate gyrus, a structure relatively resistant to hypoxic/ischemic damage.