Despite definitions in standard sources, personnel managers, psychologists, and psychometricians persistently encounter problems that are best referred to as the ambiguous nature of validity. The purpose of this article is to pro- vide an overview of construct validity and personnel testing, to demonstrate its practical utility, and to clarify with concrete examples certain theories and models, as well as to illustrate the meaning of the terminology used by com- mentators on the topic. A brief historical overview of testing and validation is presented; the progress of construct validity and its acceptance by various sec- tors of society is discussed parsimoniously in the section The Seven Wonders of Personnel Psychology. In the past, personnel psychologists have not done a very good job of understanding the constructs that underlie test perform- ance. Some new approaches can help to correct this. A process should be rou- tinely used on all tests in order to develop an understanding of the constructs that underlie performance on an employment test; only by knowing the cor- rect criterion and method of measuring it can we ascertain the intrinsic valid- ity of our measures.