Although this paper is entitled 'An anatomical commentary on the concept of infantile oral sadism' it is also an attempt to examine hypotheses regarding the sources of oral sadism. Freud did not explicitly refer to an oral sadistic phase of development in early infancy, believing as he did that sadism was a component instinct. Abraham postulated that oral sadism arises when the teeth erupt and the jaw muscles function. Melanie Klein, however, came to claim that oral sadistic impulses operate from birth and arise from the infant's innate potential for fantasy. This hypothesis is akin to Freud's theory of primal fantasies. The anatomical record supports Abraham's theory of the source of oral sadism.