This chapter opens with an account of the introduction of evidence based medicine in the 1970’s and 80’s by British epidemiologist, Archibald Cochrane, and Canadian epidemiologist, David Sackett, and his colleagues at McMaster University. The Cochrane Collaboration was established by Sir Iain Chalmers in 1993, five years after Cochrane’s death and in his honour. The section on evidence continues with a discussion of trials in medicine, including randomised controlled trials, and then reviews the history of the use of data to inform public health and medical care from ancient times to Florence Nightingale in the nineteenth century. There is section on statistics and those who introduced the various methodologies upon which today’s evidence is based. The chapter closes with a historical section on medical ethics, the introduction of informed consent, landmark cases in medical litigation to the current status of shared decision making in the third decade of the 21st century.