There are few attachment-based measures designed for use by therapists to inform the clinical process of psychotherapy. The aim was to develop an attachment based interview schedule for use by mental health professionals. A draft interview schedule was developed through a review of the literature. Systematic analysis of case materials led to refinements of the schedule. Attachment formulations were developed for six patients. The clinical validity of these formulations was assessed through group discussion and via reports from the patients' therapists. The schedule provided information about patients' attachment histories, styles, issues and problems leading to an attachment formulation, possible foci for therapeutic work, and difficulties that might arise during therapy. The interview schedule allows a picture to be built up of how attachment patterns and behaviours have developed and how they are expressed in the present. It leads to hypotheses about what needs to change for the individual to have more secure, less distorted relationships and what problems may be encountered during therapy.