Heart rate variability is a noninvasive index of the neural, especially parasympathetic, activity of the heart. Autonomic neuropathy is frequently observed in diabetic patients, and a 5-year survival rate of this kind of patient is low. To evaluate autonomic neuropathy in diabetic patients, 35 diabetic patients (proliferative retinopathy: 14, neurogenic bladder:8, postural hypotenion:6) measured for RR intervals and Valsalva ratios compared with 77 persons of the normal control group. RR variations (standard deviation: SD, coefficient of variation: CV, max-min, max/min) during deep respiration and Valsalva ratios (Vmax-Vmin, Vmax/Vmin) during Valsalva maneuver were significantly lower in the diabetic patients than in the normal control group (p<0.001, respectively). RR variations and Valsalva ratios decreased progressively with an increase of age in the control group and in diabetic patients (p<0.001, respectively). RR variations and Valsalva ratios were significantly lower in the diabetic patients with retinopathy, neurogenic bladder, and postural hypotension compared to diabetic patients without such conditions (P value <0.01, <0.05, <0.05, respectively). It is concluded that diabetic autonomic neuropathy can be indicated by the measurement of RR variations and Valsalva ratios.