Hundreds of clinical trials of potential treatments and vaccines for the "coronavirus 19 disease" (COVID-19) have been set up in record time. This is a remarkable reaction to the global pandemic, but the absence of a global coordination of clinical research efforts raises serious ethical concerns. Some COVID-19 patients might carry the burden of clinical trial involvement even though their trial cannot be completed as researchers are competing for patients. A shortage of medicines can occur when existing drugs are diverted for clinical trials. Research ethics committees are overburdened with multiple applications. A multitude of trials can also overstretch medical staff and risk neglecting non-COVID-19 patients. And finally, conflicting conclusions from a multitude of heterogeneous trials might lead to delays in public health decisions about life-saving issues. These challenges are made worse by the unpredictable evolution of epidemics, the active involvement of political decision-makers in scientific issues and the pressure of social media globally. While freedom to conduct research must be safeguarded, global health emergency situations would greatly benefit from effective international coordination mechanisms for clinical research.