The neuromatrix theory of pain proposes that pain is a multidimensional experience produced by characteristic "neurosignature" patterns of nerve impulses generated by a widely distributed neural network--the "body-self neuromatrix"--in the brain. These neurosignature patterns may be triggered by sensory inputs, but they may also be generated independently of them. Pains that are evoked by noxious sensory inputs have been meticulously investigated by neuroscientists, and their sensory transmission mechanisms are generally well understood. In contrast, chronic pain syndromes, which are often characterized by severe pain associated with little or no discernible injury or pathology, remain a mystery. The neuromatrix theory of pain, however, provides a new conceptual framework that is consistent with recent clinical evidence. It proposes that the output patterns of the neuromatrix activate perceptual, homeostatic and behavioral programs after injury or pathology, or as a result of multiple other inputs that act on the neuromatrix. Pain, then, is produced by the output of a widely distributed neural network in the brain rather than directly by sensory input evoked by injury, inflammation or other pathology. The neuromatrix, which is genetically determined and modified by sensory experience, is the primary mechanism that generates the neural pattern that produces pain. Its output pattern is determined by multiple influences, of which the somatic sensory input is only a part, that converge on the neuromatrix.