One aspect of health care reform is the utilization of evidence-based medicine to determine standard of care. The essence is the idea that clinical decisions and the determination of standard of care need to be based on a systematic scientific review of medical and scientific literature. But what is considered standard of care is an ever-changing story rather than an absolute “truth”. Even when the “true” effect remains constant, statistical inference about that medical treatment changes as evidence becomes more refined and focused. a. How do we determine “standard of care” in an ever evolving landscape? b. What methods are appropriate for determining “standard of care”? c.Is there a hierarchy of evidence? This may be illustrated through the evolution of knowledge about the association between hormone replacement therapy and the risk of coronary heart disease in post-menopausal women.