Thiolepta (alpha-lipoic acid preparation) was used in treatment of 205 patients, 134 women and 71 men, mean age 59.3±10.1 years; 196 patients with diabetes mellitus (DM) type II and 9 patients with DM type I. Treatment duration was 4 weeks. Dosage of the drug was 600 mg daily. Patients were assessed neurologically and with psychometric scales. Special attention was drawn to the severity of positive and negative symptoms of neuropathy and sleep disorders. The results demonstrated the efficacy of thiolepta in diabetic polyneuropathy assessed by all parameters. The effect remained during 3 months after the end of treatment. Good tolerability and safety of the drug are highlighted.