It is not uncommon for multiple clinical trials at the same institution to recruit concurrently from the same patient population. When the relevant pool of patients is limited, as it often is, trials essentially compete for participants. There is evidence that such a competition is a predictor of low study accrual, with increased competition tied to increased recruitment shortfalls. But there is no consensus on what steps, if any, institutions should take to approach this issue. In this article, we argue (...) that an institutional policy that prioritises some trials for recruitment ahead of others is ethically permissible and indeed prima facie preferable to alternative means of addressing recruitment competition. We motivate this view by appeal to the ethical importance of minimising the number of studies that begin but do not complete, thereby exposing their participants to unnecessary risks and burdens in the process. We then argue that a policy of prioritisation can be fair to relevant stakeholders, including participants, investigators and funders. Finally, by way of encouraging and helping to frame future debate, we propose some questions that would need to be addressed when identifying substantive ethical criteria for prioritising between studies. (shrink)