The Trinitarian view of validity (namely content, criterion-related, and construct) has dominated psychology for almost a half century. In industrial and personnel psychology especially, content and criterion-related (in particular) forms of validity have served as workhorses. Such a limited focus has lead to a stagnation of the area and the inability to incorporate more theory into the research and practice of personnel psychology. Therefore, we review the evolution of the concept of validity in the psychology discipline, with a particular emphasis on industrial and personnel psychology. We then review the legal and statutory history within industrial and personnel psychology that has helped to shape the concept of validity over the years. Finally, we examine some emerging trends in industrial and personnel psychology, including the issue of graduate training, which may have important consequences on how we conceptualize validity in the future in both our research and practice of personnel psychology.The term "validity" in psychological measurement has traditionally been conceptualized using a Trinitarian distinction among content, criterion-related, and construct validity. While calls for abandonment of the Trinitarian view of validity have been sounded for more than two decades (e.g., Guion, 1980;Landy, 1986;Schmitt & Landy, 1993;Tenopyr, 1977), in practice this view of validity still predominates. A logical question is why? Therefore, we will outline the history of validity and how it has evolved in the psychological literature up to the present time, with a particular emphasis on personnel and industrial psychology. In addition to the Trinitarian test validation view, we will examine other common references and terms for validity (e.g., consequential validity, face validity, factorial validity) and their influence on how the concept of validity has evolved in the psychological measurement literature, as well as in applied industrial settings.In addition, given the strong legal constraints that personnel psychologists must work under, we review the legal cases and regulatory decisions that have helped to shape the concept of validity over the years. For example, the Civil Rights Act of 1964 and the subsequent publication of the Uniform Guidelines on Employee Selection Procedures (UGESP) have for all practical purposes dictated how selection validation research is performed, to be legally defensible, in that the UGESP is given heavy weight in most selection discrimination lawsuits.