Charcot's or neuropathic osteoarthropathy is one of the most debilitating orthopedic sequelae of diabetes mellitus. Distinguishing Charcot's neuroarthropathy from clinically similar conditions may be challenging. The neurovascular theory postulates that Charcot's neuroarthropathy may be secondary to sympathetic denervation of the lower-extremity vasculature. A convenient method for assessing autonomic neuropathy in patients with Charcot's neuroarthropathy is needed. Short-term power spectral analysis (PSA) of heart rate variability (HRV), a noninvasive and quantitative method for assessing autonomic neuropathy, may be advantageous compared with the traditionally used Ewing's cardiovascular reflex tests. However, there are limitations to the clinical use of PSA of HRV because of poor standardization. We standardized PSA of HRV and assessed autonomic neuropathy in 17 people with acute Charcot's neuroarthropathy using PSA of HRV versus Ewing's tests. More patients with Charcot's neuroarthropathy were diagnosed as having autonomic neuropathy with PSA of HRV than with Ewing's tests (94% versus 82%); however, no significant difference between the two methods was found. The results of this study suggest that PSA of HRV requires minimal patient collaboration and time expenditure compared with Ewing's tests and may be useful in detecting autonomic neuropathy in patients with Charcot's neuroarthropathy.