In this article, the separate histories of validity and factor analysis are reviewed, as well as some of the ways in which factor analysis has become such a widely used technique for an estimation of construct validity. From a historical perspective, 4 eras, in terms of definitions of validity, are identified; current views emphasize the validity of inferences drawn from scores, the conceptualization of validity as a unitary concept, and the need to include the study of the consequences of test use. The history of factor analysis dates back to the early 1900s. Important developments in its history are reviewed, including the distinction between exploratory and confirmatory factor analysis. Finally, some recommendations for the appropriate use of factor analysis are offered, as well as cautions against overreliance on factor analysis in the estimation of construct validity.