 Clinical trials are essential for evaluating the effectiveness of treatments and interventions. However, it is important to ensure that the outcomes being measured are relevant and important to those who will make decisions based on the trials results. This can be achieved by developing a core outcome set, COS, which is a list of outcomes that should be measured and reported in all trials for a given clinical area. A COS should be developed with input from multiple stakeholders, using a consensus-building approach such as Delphi or Nominal Group technique. Once a COS is established, it can be used to guide the design of future trials and help ensure that the most important outcomes are measured and reported. This article was offered by Williamson Pauler R., Autman Douglas G., Blaisby Jane M., and others.