Cannot simply be considered as a nociception phenomenon: it is more complex than a simple transmission system that conveys this information to the cerebral cortex. It is mainly a psychological event. Numerous regulating and inhibiting effects on incoming pain signals exist, for the most part located in spinal and thalamic areas; only half of these are morphine-dependent. Knowledge of these allows a better approach to chronic pain, using not only medication but also other techniques such as physiotherapy and music therapy analgesia.