Eleven diagnosed diabetic patients and fifteen healthy age-matched control subjects were subjected to six standardized cardiovascular autonomic reflex function tests. The aim of the study was to identify the best sympathetic and parasympathetic autonomic function tests in diabetic patients and to determine their sensitivity. Several diabetic patients showed an abnormal response to various autonomic function tests. Among the three sympathetic tests studied, the coefficient of variation of all tests was found to vary; hence, the most sensitive test could not be determined. The heart-rate response to standing was found to be the most sensitive as it showed the lowest coefficient of variation. More parasympathetic than sympathetic tests showed abnormal responses in diabetics, particularly for heart rate responses to a deep breathing test. The results indicate that all autonomic function tests have to be performed for a proper evaluation/diagnosis of diabetic autonomic neuropathy.