Transcranial direct current stimulation (tDCS) is a noninvasive technique of neuromodulation that is currently studied as a possible therapeutic tool for several neurological and psychiatric diseases and has been found safe and well tolerated. Based on experimental evidence in animals and human subjects, tDCS is expected to reduce motor cortex excitability and excitotoxicity, that is neuronal injury induced by excessive glutamatergic stimulation, one of postulated pathophysiological mechanisms in ALS.