This paper provides a brief overview of attachment theory in order to describe the genesis of attachment disorganization. All infants develop an attachment style as an adaptive response to their caregiver's behaviour, and the overall pattern may be secure or insecure. However, the coherence of any of these infant attachment patterns can break down resulting in attachment disorganization. This paper describes the characteristic behaviour of the disorganized infant and discusses the validity of the concept in terms of the ability of the disorganized classification to predict future infant behaviour. We explain how parental state of mind may lead to infant disorganization and describe the parental behaviours that are thought to be associated with this adverse infant development. Finally, we discuss the observable developmental phenomena of attachment disorganization in terms of psychoanalytic theory.