The objective of the study was to evaluate the prevalence of and the factors associated with cardiovascular autonomic diabetic neuropathy (CADN) and peripheral neuropathy in patients attending clinical and outpatient diabetes centers. The design was a multicenter cross section study with random selection of patients with Type 1 or Type 2 diabetes from seventeen German, three Swiss, and two Austrian inpatient and outpatient diabetes centers. A total of 1,642 patients were recruited, 1,171 of whom (Type 1: n = 647, age: 11-69 years; Type 2: n = 524, age: 16-72 years) were studied. Measurements and results. The following six autonomic function tests based on heart rate variation were used for the diagnosis of CADN: coefficient of variation and power spectrum in the low- and mid-frequency bands at rest, mean circular resultant during deep breathing, Valsalva ratio, and max/min 30:15 ratio to standing. The age-dependent lower limit of the normal range in these tests had previously been defined at the 2.3 centile in 120 healthy subjects. Definite CADN defined by the strict criterion of abnormal results in > or = 3 of these 6 tests was detected in 16.8% of the Type 1 and 22.1% of the Type 2 diabetic patients (p < 0.05). The corresponding rates of borderline CADN defined as the presence of 2 abnormalities were 8.5% and 12.2%, respectively (p < 0.05). Peripheral neuropathy defined as the presence of > or = 2 abnormalities among 3 criteria (neuropathic symptoms, absent tendon reflexes, and abnormal malleolar vibration perception threshold) was observed in 17.1% of Type 1 and 34.8% of Type 2 diabetic patients (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)