Construct validity of an interview measure of personal initiative (PI) is examined in two parts. The first part assembles the results from 11 samples, showing that PI is meaningfully related to a nomological network of variables, based on environmental supports; knowledge, skills, and cognitive abilities; personality variables and orientations; and behavior and performance, confirming our hypotheses. In the second part, the article presents a new analysis that looks at the influence of motivational parameters (control aspiration, self-efficacy, and change orientation) and cognitive ability on PI within a longitudinal study in East Germany.