It has been reported that diabetic polyneuropathy treatment with alfa-lipoic acid may improve the subjective complains of limbs pain and paresthesias. However it is controversial if the objective neurological symptoms of the polyneuropathy are improved. Although the electroneurography is more precise method for diagnosis and follow up of the polyneuropathies the published results regarding alfa-lipoic acid are also controversial. The aim of this examination was to evaluate the efficiency of alfa-lipoic acid treatment of diabetic polyneuropathies using electroneurographic examination. Thirty patients with clinical data for symmetric distal diabetic neuropathy were examined. The motor conduction velocities and M-wave amplitudes after fibular and tibial nerve electrostimulations were examined. The sensory nerve action potentials after sural and median nerve stimulations were also examined. The electroneurographic examinations was performed before and after treatment. The alfa-lipoic acid (Thioctacid) was applied as a 1200 mg daily intravenous infusion for 30 days, followed by 60 days oral intake of 600 mg daily. The distal motor latencies of the tibial and fibular nerves were shortened significantly after the treatment, while no changes in M-wave amplitude or motor conduction velocities were found. The distal latencies and the amplitudes of the sensory nerve action potentials were not significantly different after treatment. In conclusion our results revealed that high doses alfa-lipoic acid may improve the peripheral nerves function in patients with diabetic neuropathy. The controversial results were probably caused by the small number of patients and the short treatment duration.