The article provides the historical roots and rationale for providing professional psychologists with knowledge of the underpinnings in core scientific areas of psychology with two goals–knowledge of those scientific areas themselves and as the basis for further understanding the integration of science and practice to improve professional service delivery. This article discusses the early roots of the applied areas within psychology and the changes in curricular expectations in accreditation to the current provisions for the accreditation of doctoral programs in professional psychology. After the historical introduction, the article discusses the current use of the concept of broad and general training as the basis for current practice in accreditation of programs in professional psychology and for the practice as a licensed psychologist. Finally, the article provides some initial discussion of the different perspectives in the rest of the section regarding how best to provide students with appropriate knowledge for competence in scientific underpinnings of professional psychology. (PsycINFO Database Record (c) 2011 APA, all rights reserved)