Complete dentures need to be replaced at suitable intervals-either because of changes in the denture-bearing tissues, usually due to alveolar resorption, or because of general deterioration of the existing dentures. The purpose of this and the following article is to consider the challenges that arise in replacing complete dentures. The rationale for using techniques in which features of existing dentures can be employed in the construction of replacement complete dentures will be discussed, together with methods suitable for clinical practice. In the first part diagnosis and treatment planning will be considered and a variety of copying techniques reviewed. The limitations of these techniques will be discussed and alternative treatment strategies will be considered.