This review shares a perspective that the history of medicine provides numerous examples of how emerging illnesses develop from sound therapeutic efforts. The author discusses more than 40 distinct entities that resulted from new and existing medication therapies. Many of these continue to treat one illness but place patients at risk for developing a secondary condition. This article provides readers with a fascinating historical perspective, one that not only raises concern over all currently available novel therapies but also may lead to undiscovered and unintended conditions.