Eight tests for cardiovascular reflex function were evaluated in a group of 140 diabetic patients. The sensitivity, reproducibility and normal values of each test were previously assessed in a group of 70 normal controls. The measure of the R-R interval variation during six cycles of deep breathing (expiration/inspiration ratio) proved to be the most sensitive test, and was selected for screening. The Valsalva ratio, the bradycardia/tachycardia ratio post-standing and the blood pressure response to standing and to sustained handgrip served as a confirmatory test of autonomic neuropathy and were related to the severity of the lesion. The R-R interval variation during one deep breathing cycle, the post-standing tachycardia, and the R-R 30/15 standing ratio proved to be of little or not value in assessing cardiovascular neuropathy. Cardiovascular autonomic neuropathy was diagnosed in 38.5% of our diabetic population, predominantly in patients with other clinical evidence of autonomic neuropathy. In a few asymptomatic patients, abnormal cardiovascular responses were the first evidence of autonomic lesion.