This article reviews the peripheral and central mechanisms of neuropathic pain. The main mechanisms involved in neuropathic pain are: (1) ectopic activities, (2) ephapses, (3) sensitization of nociceptors. Central morphological alterations could also be involved: (1) medullar neuronal reorganization, (2) hyperexcitability of central nervous system nociceptive neurones. The relative resistance of these neuropathic pains to opioid drugs could be related to a decrease in the number of opioid receptors to an amino acid mediator related spinal neurons hyperexitability and to an increase in non opioid peptides such as cholecystokinin.