In order to elucidate the clinical characteristics of diabetic autonomic neuropathy, we assessed sympathetic and cardiovagal functions in diabetic patients. The following non-invasive autonomic tests were performed on examined in eleven healthy men and eight male diabetic patients. I. Sympathetic vasomotor functions: 1 Fall in blood pressure during head-up tilt. 2 Change in blood pressure during the Valsalva maneuver. II. Sympathetic sudomotor function.: Quantitative sudomotor axon reflex test on the legs and forearms. III. Cardiovagal functions: 1 Coefficient of variation in R-R intervals in ECG with patient at rest and during deep breathing(6 breaths/min), 2 Valsalva ratio. Whole autonomic nerve functions (sympathetic vasomotor, sympathetic sudomotor, and cardiovagal function) were reduced in the diabetic patients compared to the healthy controls. Sympathetic functions (vasomotor and sudomotor) in the patients with diabetic foot lesions were significantly deteriorated compared to those in patients without. The severity of cardiovagal dysfunction between the two groups of patients with and without foot lesions was not significant. These findings suggest a close relation between the causes of diabetic foot lesions and sympathetic dysfunction.