Purpose Increased oxidative stress and impaired antioxidant defense are important mechanisms in the pathogenesis of diabetic myopathy. Since diabetes mellitus type 1 decreases muscle regeneration capacity the present study was designed to determine the influence of alpha- lipoic acid (ALA), a potent biological antioxidant, on the process of regeneration of diabetic rat skeletal muscles. Methods 40 Wistar rats were divided into three groups: control (n = 8), untreated diabetic group (n = 16) and ALA treated diabetic group (n = 16). The regeneration process was provoked in streptozotocin- induced diabetic rats in both slow (m.soleus, SOL) and fast (m.extensor digitorum longus, EDL) skeletal muscles by intramuscular injection of myotoxin bupivacaine. At intervals of 10 days and 4 weeks, muscle histochemical and morphometrical analysis (fiber cross areas and fiber type distribution) was performed. Results Changes induced by diabetes are evident in redistribution of muscle fibers and in significant level of atrophy. After 4 weeks of diabetes, glycolytic muscle fibers are dominant in both slow and fast muscles. Muscle atrophy is present in all fiber types except in type I of slow skeletal muscle. Treatment with ALA reduce changes in the morphological properties caused by diabetes mellitus type 1 in slow and fast rat skeletal muscles during the process of regeneration. Conclusion Treatment with lipoic acid during 4 weeks has shown effects on the redistribution of muscle fibers, and can prevent atrophy in slow and fast diabetic muscle