The paper describes an application of child psychotherapy in a paediatric setting. It examines the crucial part that attention to endings played in a clinical intervention where the phantasy of going on for ever threatened to inhibit growth. Case material is used to illustrate the different meanings and functions of endings and their significance in terms of parenting issues and developmental tasks. In this context the concept of negative elasticity is put forward as a useful tool for exploring the nature of boundaries. The final part of the paper focuses on the value of the external-reality experience of ending, its relationship to potential professional omnipotence and the importance of sustaining a tension between inner- and outer-world factors.