Studies in animals and in patients have suggested that magnesium (Mg), a physiological blocker of N-methyl-D-aspartate receptor, could have an antinociceptive effect in painful situations. This randomised, double-blind, controlled trial in two parallel groups aims at studying oral Mg effects in patients with neuropathic pain. It explores the impact of Mg (6x419 mg Mg chloride/capsule per day for a month), versus placebo (lactose) on pain [Neuropathic Pain Symptom Inventory (NPSI) and numerical scale (NS)], and on quality of life indicators after 4 weeks treatment, in 45 patients suffering from neuropathic pain. After 4 weeks, NPSI, NS and quality of life are not different in the Mg and placebo groups, while the frequency of pain paroxysms diminishes and the emotional component improves in the Mg group compared to baseline. This clinical trial displays a large placebo response and could not demonstrate any significant difference in pain alleviation after a month of oral treatment between Mg and placebo in patients suffering from neuropathic pain. Frequency of pain paroxysms and emotional impact will be explored in future studies as they constitute major aspects of pain alleviation in chronic pain conditions.