Encapsulation is defined as a defence against annihilation anxiety. A theoretical orientation concerning the origins of this kind of anxiety is outlined, and the causal efficacy of early traumata is emphasized. On this basis, encapsulation is conceptualized as an introjective process through which attempts are made to fuse and confuse parts of the self with parts of the lost and abandoning object. Clinical and case history data from several patients are presented. A number of topics for further research are suggested. The literature is reviewed, and the current use of 'encapsulation' is linked to earlier work on disavowal, foreclosure and resourceless dependence.