OBJECTIVE: Low heart rate variability (HRV) is, in several patient groups, related to poor prognosis. The underlying mechanisms are still unclear. The aim was to study if there is a relationship between HRV, which is a measure of baroreceptor function, and atherosclerosis. DESIGN: The relationship between heart rate variability and carotid arterial wall stiffness was studied in subjects with type 1 diabetes mellitus in which autonomic dysfunction and early atherosclerosis are common. HRV was assessed from power spectral analysis of 24-h Holter recordings and arterial wall stiffness was assessed from an ultrasound study of the right common carotid artery. SETTING: A university hospital. SUBJECTS: Fifty-nine patients (41 +/- 8 years) from the Stockholm Diabetes Intervention Study (SDIS) were investigated. These patients were randomized to intensified conventional treatment or standard treatment approximately 12 years before this study. RESULTS: Patients with stiffer arteries had lower HRV in all spectral bands (r = -0.32 to -0.40, P = 0.06-0.001). This relation remained on correcting for age. All spectral parameters of HRV correlated with the mean HbA1c from 10 years of study (r = -0.37 to -0.40, P = 0.004-0.001). CONCLUSIONS: In patients with type 1 diabetes mellitus, heart rate variability and arterial wall stiffness are related to each other. The results suggests that the autonomic nervous system could be a link between diabetes and vascular disease.