Glucose counter-regulation during insulin-induced hypoglycaemia was studied in Type 1 diabetic patients without evidence of autonomic neuropathy and compared with that of a non-diabetic control group. The glucose recovery rate following hypoglycaemia was delayed in the diabetic compared with the control subjects and this was most pronounced for the initial, rapid phase of glucose increase (glucose increase in 15 min, control: 1.1 +/- 0.1 versus 0.4 +/- 0.1 mmol/l; p less than 0.01). The release of glucagon during hypoglycaemia was blunted in the diabetic patients (maximal plasma levels, control: 148 +/- 25 versus 70 +/- 10 pg/ml; p less than 0.01). The adrenaline levels were also lower compared with the control subjects (maximal plasma levels, control: 7.23 +/- 1.21 versus 3.27 +/- 0.87 nmol/l; p less than 0.05). To evaluate the importance of the blunted glucagon response for the delayed glucose compensation, glucagon was infused during the hypoglycaemia. Overall glucose recovery rate was improved but did not return to normal. Consequently impaired glucagon release in the diabetic patients cannot alone explain impaired glucoregulation; the lower adrenaline levels and/or an effect of the previous glucose levels per se on hepatic glucose production are probably also of importance.