We expect medicine to progress in an orderly fashion, with good medical practices being replaced by better ones. But some tests and therapies are discontinued because they are found to be worse, or at least no better, than what they replaced. Medications like Vioxx and procedures such as vertebroplasty for back pain caused by compression fractures are among the medical advances that turned out to be dangerous or useless. What Dr Vinayak K Prasad and Dr Adam S Cifu call medical reversal happens when doctors start using a medication, procedure, or diagnostic tool without a robust evidence base-and then stop using it when it is found not to help, or even to harm, patients. Drs Prasad and Cifu narrate fascinating stories from every corner of medicine to explore why medical reversals occur, how they are harmful, and what can be done to avoid them. They explore the difference between medical innovations that improve care and those that only appear to be promising. They also outline a comprehensive plan to reform medical education, research funding and protocols, and the process for approving new drugs that will ensure that more of what gets done in doctors' offices and hospitals is truly effective.