It has been suggested that subclinical signs of neuropathy appear earlier than microvascular complications of diabetes. To evaluate the occurrence of autonomic nervous system dysfunction in the early stage of childhood diabetes, subclinical signs of autonomic neuropathy (resting heart rate, hyperventilatory arrhythmia, standing/lying heart rate ratio, orthostatic decrease in blood pressure, and increase in blood pressure during sustained handgrip) were investigated in 54 children with type 1 diabetes divided into three groups: 14 recent-onset diabetics (3 weeks after the diagnosis), 20 diabetics in the remission phase, and 20 patients after the remission phase. 30 healthy age-matched children were used as control group. The mean resting heart rates of the diabetic groups in the remission phase and after the remission phase were significantly higher than those in the healthy control group (81.7 ± 5/min and 88.5 ± 6/min vs. 72.2 ± 8/min; p < 0.01). The hyperventilatory arrhythmia in the group of diabetic children after the remission phase in comparison with the control group was significantly decreased (29.1 ± 4/min vs. 22.7 ± 3/min; p < 0.01). In a few cases of the recent-onset diabetic group, the increase in resting heart rate, the decrease in hyperventilatory arrhythmia, and the standing/lying heart rate ratio proved to be significant. In the remission phase, the same parameters showed abnormal values in one third to one fifth of the children. In the diabetic group after the remission phase, these parameters were established as pathologic in one half to one fifth of the children, and in some cases, the orthostatic decrease in blood pressure and the increase in blood pressure during sustained handgrip were pathognomic as well. These results indicate that the initial, functional disturbances of the autonomic nervous system may appear early during the course of childhood diabetes and they emphasize the necessity to search for subclinical neuropathy in diabetic children.