A 16-month-old child is presented who developed severe "stress hyperglycemia" with the onset of a respiratory distress syndrome. The serum glucose rose from 74 mg/dl to 520 mg/dl and returned to 52 mg/dl all within 24 h. These variations in serum glucose were paralleled by a similar marked increase in plasma cortisol concentration (from 41 to 90 to 36 micrograms/dl). The patient was receiving no iv dextrose and required no exogenous insulin. These data are consistent with a diagnosis of stress hyperglycemia. This report is unique in that, to our knowledge, stress hyperglycemia to levels greater than 350 mg/dl have not been previously reported in either adults or children.