Interpersonal psychotherapy is an evidence-based therapy, originally developed to treat major depression. It is cited in numerous good practice guidelines. The biopsychosocial signs of depression are understood in the context of current social and interpersonal stressors, defined in terms of role transitions, disputes, bereavements and sensitivities. In therapy, the patient learns to understand the interactions between symptoms and interpersonal difficulties and the ways in which they are mutually reinforcing. Patients are helped to break this pattern and achieve a reduction in depressive symptoms and improvement in interpersonal functioning through improved communication, expression of affect and proactive engagement with the current interpersonal network. The therapeutic relationship is used as a tool for exploring and modelling external relationships. This article outlines the background to interpersonal psychotherapy, the process of therapy and the expansion of the evidence base.