BACKGROUND: Alpha-Lipoic acid (ALA) administration has been reported to ameliorate some of symptoms of peripheral polyneuropathy in diabetic patients and to improve endoneurial nutritive neural blood flow and nerve conduction velocity in diabetic rats. But it is not clear whether ALA has the preservation effect on epidermal nerve fibers (ENFs) density. METHODS: We tested the efficacy of ALA in preserving current perception thresholds (CPTs) and ENFs (numbers/mm) in OLETF (Otsuka Long-Evans Tokushima Fatty) rats, an animal model of type 2 diabetes, which were fed with sucrose until diabetes mellitus developed. Thereafter, one group of OLETF rats was fed with ALA and the other was not for 40 weeks. Diabetic rats were administered with ALA (80 mg/kg of body weight/day) by oral feeding for 40 weeks. The effect of ALA treatment on ENFs preservation was assessed by protein gene product 9.5 immunostaining. Quantification of neuropathic symptoms on the dorsum of hind paws of rat was measured by CPT test every 4 weeks. RESULTS: Numbers of ENF significantly decreased in OLETF rats fed without ALA compared with OLETF rats fed with ALA (P < 0.01). The thresholds at 2000, 250 and 5 Hz in OLETF rats fed with ALA did not increased and OLETF rats without ALA significantly increased at 80 weeks (P < 0.01). CONCLUSION: These observations suggest that administrations of ALA may be useful for preserving ENFs and CPTs in OLETF rats dorsum of hind paws skin.