A literature review was performed on the subject of defensive medicine, in order to gather information and evidence for identifying a shared definition of this phenomenon, identify its causes, quantify its frequency and its economic impact.Results show that defensive medicine is primarily the result of medical professionals adapting to the pressure of litigation risks, and whose behaviour is motivated by fear of malpractice claims rather than by the patient's health. Defensive medicine seems to have become a diffuse phenomenon, afflicting all diagnostic-therapeutic areas and some disciplines to a greater degree, and leading to a large waste of human, organizational and economic resources.