This paper introduces a Journal of Organizational Behavior point/counterpoint exchange (this issue) that focuses on the appropriate level of aggregation primarily in the assessment of personality in general and core self-evaluations (CSE) in particular. Gilad Chen reviews arguments for and against the higher-order construct of CSE, offering a number of recommendations for strengthening it. Timothy Judge and John Kammeyer-Mueller offer a defense of CSE, and then extend the discussion to the measurement of other constructs beyond the personality domain. Together these two papers provide important insights about the appropriate level of aggregation of individual measures, and situations in which higher-order versus lower-order measures might be preferred. Copyright © 2011 John Wiley & Sons, Ltd.