Emphasize evidence from direct (“head-to-head”) comparisons, effectiveness in real-world health care settings, health care outcomes (as opposed to surrogate or other intermediate endpoints), and ability to identify different treatment effects in patient subgroups -reflects the demand for a real world evidence to support practical decisions -used because of increasing cause of conducting clinical trial --can draw on variety of complementary study designs and also analytical methods -useful in gradual increase in use of electronic health records and more powerful in computing and related health information technology