This study involves four stages for the development of a COS. Initially, a systematic review of the literature will identify the outcomes measured in existing peer reviewed and grey literature. A second stage will determine patient- and proxy-defined outcomes of care at the end of life through quantitative and qualitative methodologies. This step will be duplicated in several countries. Thirdly, from a list of salient outcomes identified through stages 1 and 2, stakeholders will be asked to rank the importance of the preselected outcomes in order to prioritise outcomes through a Delphi process. Lastly, a face-to-face consensus meeting will take place in order to define, propose and endorse the core outcome set.