In a letter published last month in The Lancet, doctors, scientists, and bioethicists from a wide range of countries – including Guinea, Ghana, Nigeria, and Senegal, as well as Britain, France, Hong Kong, and the United States – argued that a randomized trial is justified only when there is “equipoise,” or balance, between the two options offered. This can happen when doctors do not know whether a proposed treatment will do more harm than good, or when they are in doubt about which of two treatments is more likely to cure the patient.