The aim of this special issue is to examine methods for assessing and treating attachment disorders. This target article outlines existing strategies for assessment and considers which aspects of severe attachment disturbances and disorders may be core features of the disturbance(s). The usefulness of alternative methodologies for assessment are discussed, with particular emphasis on the need for the development of clinical protocol. The applications and implications for treatment are then discussed, with particular emphasis on the nature of the underlying disturbances that should be a focus for intervention. An absence of established treatment guidelines or consensus regarding the mechanisms of change are highlighted as barriers to further progress.