Background – A composite endpoint is often used as the primary endpoint to assess the efficacy of a new treatment in randomized clinical trials (RCT). In cardiovascular trials, the often rare event of the relevant primary endpoint (individual or composite), such as cardiovascular death (CV death), Myocardial Infarction (MI), or both, is combined with a more common secondary endpoint, such as target lesion revascularization, with the aim to increase the statistical power of the study. Methods – Gómez and Lagakos developed statistical methodology to be used at the design stage of a RCT for deciding whether to expand a study relevant primary endpoint e1 to e*, the composite of e1 and a secondary endpoint e2. The method uses the asymptotic relative efficiency of the logrank test for comparing treatment groups based on e1 versus the logrank test based on e*. The method is used to assess, in the cardiovascular research area, the characteristics of the candidate individual endpoints that should govern the choice of using a composite endpoint as the primary endpoint in a clinical trial. Results and conclusions – A set of recommendations is provided based on the reported values of the frequencies of observing each candidate endpoint as well as on the magnitude of the effect of treatment as expressed by the hazard ratio, supported by cardiovascular RCTs published in 2008.