The purpose of this paper is to analyse the concept of 'best interest' in order to give nurses, who use it to justify their actions, a clear picture of what this means, and to identify the skills needed for doing so. The process for concept analysis developed by Walker and Avant was used in the analysis of data generated from the literature. Themes were identified from which the defining attributes, antecedents and consequences emerged. The congruence of the findings with current values in nursing, such as promotion of patient autonomy, and the nurse as advocate, are discussed, together with the underpinning ethics theory. The skills needed for nursing practice are identified and recommendations for nurse education are made.