Randomized controlled trials (RCTs) are a useful tool to check the effectiveness of drugs but have come to shape the culture of medicine in a manner that increasingly compromises medical care. Dependence on RCT evidence is compromised by the well-known problems stemming non-publication of trials, lack of access to trial data, ghostwriting of those trials that are published and a variety of coding and other strategies to hide harms. But what is less appreciated is that whenever a drug and an illness can produce the same benefit or harm that the outcomes of RCTs can be profoundly misleading. This article gives examples of how RCTs can produce the wrong answer.