Lay summaries of Phase I trials in healthy volunteers pose a challenge because their endpoints are complex, the targeted indication may not be known when they are conducted, their results are often reported years after the trial ended, and the majority of substances tested in Phase I never reach the market. Nevertheless, the European Union Clinical Trials Regulation (EU CTR) mandates that lay summaries are to be provided for all clinical trials regardless of clinical phase. As lay summaries are intended to inform the public about the results of clinical studies, they need to be understandable to people without specific knowledge of the disease or the clinical research process. It is challenging to write lay summaries for Phase I trials that are both meaningful for the public and in line with the requirements of the EU CTR. We have developed a template to facilitate writing of lay summaries of Phase I trials in healthy volunteers. Using a template ensures that study designs and endpoints are described in a consistent lay-friendly manner across different types of Phase I trials.