Undertaking assessment is a significant component of a Child Psychotherapist's work within Child and Adolescent Mental Health Services (CAMHS), yet as an activity it has been relatively neglected in the research literature. This study made use of a small-scale, qualitative design to explore the nature and function of psychoanalytic assessment work within a single CAMHS team. After an initial audit of child psychotherapy assessment work, indepth interviews with 5 Child and Adolescent Psychotherapists, exploring the nature of assessment work, were analysed using Interpretative Phenomenological Analysis (IPA). Results suggested that assessment is a major part of the Child Psychotherapist's work, although there are different types of assessment done in different contexts. Among the participants there was a certain shared understanding of the psychoanalytic approach to assessment, although with significant differences in regard to process, technique (e.g. use of interpretation, the role of countertransference) and the reporting of assessments. The analysis also suggested tensions between the role of the assessor as an `expert' and as a `therapist'.