Evidence-based therapies stemmed from the movement toward evidence-based medicine, and later, evidence-based practice (EBP) in psychology and allied fields. EBP reflects a progressive historical shift from naïve empiricism, which is based on raw and untutored observations of patient change, to systematic empiricism, which refines and hones such observations with the aid of systematic research techniques. EBP traces its roots in part to the development of methods of randomization in the early 20th century. In American psychology, EBP has traditionally been conceptualized as a three-legged stool comprising high-quality treatment outcome evidence, clinical expertise, and patient preferences and values. The research leg of the stool is typically operationalized in terms of a hierarchy of evidentiary certainty, with randomized controlled trials and meta-analyses of such trials toward the apex. The most influential operationalization of the EBP research leg is the effort to identify empirically supported treatments, which are psychotherapies that have been demonstrated to work for specific psychological conditions. Still, EBP remains scientifically controversial in many quarters, and some critics have maintained that the research base underpinning it is less compelling than claimed by its proponents.