Although alternative hypothesis stated that selfmutilation reflects a proclivity in some species and circumstances to shed an insensate appendage, it has been shown repeatedly, that mere chronic insensitivity of a limb does not result in selfmutilation. In the article, correlation of selfmutilation and pain sensation in animals is discussed in terms of similarities with human patients, an involvement of NMDA receptors, and key role of prior nociceptive stimulation.