Heart rate signals(HRS) have chaotic characteristics and carry information about autonomic nervoussystemic function(ANSF). Power spectral and chaotic characteristics of HRS taken from 87 patients withdiabetes mellitus(DM) were studied. The spectral and chaotic characteristics included both graphicalcharacteristics and numerical characteristics .Spectral index(TFP

PHV

PVV and RYH) values and chaoticindex (HLE

HFD

HRD and LCC)values in the DM group were significantly lower than those in the controlgroup(P＜0. 05). The results showed that damage to cardiac ANSF in DM patients probably existed and thatvagus damage was possibly more severe. The results also showed that:(1) chaotic indexes could quane possiblymore sensitive and accurate than spectral indexes in early diagnosis of autonomic neuropathy(AN). Hence

combining power spectral analysis with chaotic analysis could provide some information for the early prevention

diagnosis and treatment of AN.