The purpose of this study was to investigate the circulatory responses to hypoglycaemia in diabetic and non-diabetic children and to determine whether these changes were associated with hormone levels or clinical variables. Plasma glucose levels in 18 diabetic and 15 control children were gradually lowered to 2.5 (0.3) mmol/L (mean (SD)) and 2.9 (0.2) mmol/L, respectively. Blood pressure and heart rate were recorded at 10-min intervals, and blood samples were taken for hormone analysis. Systolic pressure increased from 110.1 (10.0) to 115.0 (11.2) mmHg (p = 0.008) in the diabetic children and from 116.9 (12.0) to 121.6 (12.7) mmHg (p = 0.049) in the controls. Diastolic pressure decreased from 61.9 (6.7) to 55.5 (7.6) mmHg (p < 0.001) in the diabetic children and from 66.5 (6.3) to 55.1 (5.1) mmHg (p < 0.001) in the controls. The increase in pulse pressure during hypoglycaemia was significantly smaller in the diabetic children (10.6 (5.5) vs. 15.7 (7.7) mmHg, p = 0.04). The final systolic and pulse pressure correlated with the final adrenaline level in the controls (r = 0.66, p = 0.008 and r = 0.70, p = 0.003, respectively). In the non-diabetic as well as the diabetic group, the increase in pulse pressure correlated with the increase in adrenaline (r = 0.66, p = 0.008 and r = 0.50, p = 0.03, respectively). It is concluded that systolic pressure increases and diastolic pressure decreases during hypoglycaemia in children. The smaller increase in pulse pressure observed in the diabetic children is probably related to a significantly smaller increase in adrenaline in this group.