AIMS: Autonomic neuropathy is a serious diabetic complication, probably contributing to the death of many young people with Type 1 diabetes mellitus. It is often not diagnosed. METHODS: Patients with Type 1 diabetes from the Stockholm Diabetes Intervention Study were investigated with power spectral analysis (n = 88), heart rate and blood pressure reactions to tilting (n = 66), and heart rate variability during deep breathing (n = 70) a mean of 11.4 years after randomization to intensified conventional treatment (ICT) or standard treatment (ST), the treatment groups similar with regard to age, duration of diabetes and metabolic control at baseline (HbA1c 9.4 (1.3)%, mean (SD)). Blood glucose levels (mean of 29 HbA1c values) during the 10 years were lower in the patients from the ICT group (7.2 (0.6) vs. 8.3 (1.0)%, P = 0.001). RESULTS: Heart rate variability (HRV) in the high frequency range (P = 0.034), the expiration-inspiration ratio (P = 0.020), and the brake index during tilt (P = 0.044) were lower in the ST group, indicating more pronounced parasympathetic insufficiency. Systolic blood pressure fell by 10 (16) mmHg in the ST group, and by 2.5 (15) mmHg in the ICT group 8 min after rising from the supine to a 70 degrees upright position (P = 0.034). A decreased autonomic function was associated with age and higher HbA1c. CONCLUSION: Better autonomic nerve function is associated with lower HbA1c and lower age which were both the same in the intensively and the conventionally treatment groups at baseline. After a mean of 11.4 years autonomic function was better in the intensively treated group.