Hypoglycemia is associated with increased activity in the low-frequency bands in the electroencephalogram (EEG). We investigated whether hypoglycemia awareness and unawareness are associated with different hypoglycemia-associated EEG changes in patients with type 1 diabetes.Twenty-four patients participated in the study; 10 with normal hypoglycemia awareness and 14 with hypoglycemia unawareness. The patients were studied at normoglycemia (5-6 mmol/l), hypoglycemia (2.0-2.5 mmol/l) and during recovery (5-6 mmol/l) by hyperinsulinemic glucose clamp. During each one-hour period, EEG, cognitive function and hypoglycemia symptom scores were recorded and the counterregulatory hormonal response was measured.Quantitative EEG analysis showed that the absolute amplitude of the theta band and alpha-theta band up to doubled during hypoglycemia with no difference between the two groups. In the recovery period the theta amplitude remained increased. Cognitive function declined equally during hypoglycemia in both groups and during recovery reaction time was still prolonged in a subset of tests. The aware group reported higher hypoglycemia symptom scores and had higher epinephrine and cortisol responses compared to the unaware group.In patients with type 1 diabetes, EEG changes and cognitive performance during hypoglycemia are not affected by awareness status during a single insulin-induced episode with hypoglycemia.