Severe hypoglycemic episodes in diabetic children are a serious complication of present medical therapy. With the recent trend towards intensified insulin therapy, the incidence of severe hypoglycemia will probably increase. The pathophysiological mechanisms in the development of severe hypoglycemia are lack of modulation of plasma insulin levels, diminished or abolished glucagon release, delayed epinephrine release, and diminished glucose threshold for awareness of hypoglycemic symptoms, especially in well stabilized diabetics. The consequences of severe hypoglycemia are EEG changes, focal or generalized convulsions, (rarely) partial or generalized epilepsy, and disturbances of cognitive function probably due to neuronal damage. Some of the risk factors can easily be understood and are preventable. A highly increased risk factor is a low HbA1, and a complete lack of endogenous insulin secretion. However, in our experience human insulin is not an additional risk factor. Home blood glucose monitoring for determining the correct insulin dose and food supply is of great prophylactic importance. In the presence of coma in a diabetic child due to hypoglycemia, i.m. glucagon or i.v. glucose should be administered immediately in the correct dose. Following a severe hypoglycemic episode the glucose equilibration should be somewhat less strict. Regular education of the patient on risk factors, prevention and therapy of hypoglycemia is of great importance.