This paper examines the relevance of attachment theory in the provision of psychological support to people who are affected by HIV. It highlights the themes of change, loss and vulnerability as central to the issues which confront members of this client group. Indications are provided of a range of attachment-related behavioural responses which can be activated by these conditions, and illustrations are provided of how the activation of attachment behaviour can destabilize the relationships of some clients who are anxiously attached. The concept of a secure base, a term first coined by Mary Ainsworth and developed as a theme by the originator of attachment theory, John Bowlby, is presented as being a central provision by the therapist in work with clients who are affected by HIV, and illustrations are given of how the therapist might begin to help build a secure base for clients who have anxious, internal working models of attachment. The paper concludes with an indication of how an attachment-based approach might be used in working with clients in the terminal stages of HIV-related illness.