Abstract. Core self-evaluations (CSEs) represent a prominent construct with links to a number of important organizational behaviors and outcomes. Previous research on this variable appears to have assumed that CSE is a stable trait. However, very little research has examined this assumption, particularly over longer time periods. This study investigated this issue, focusing on within-person variability in CSE. Drawing from several theoretical perspectives related to self-concept, we examined the extent to which levels of this construct varied over several years as well as potential predictors of this variability. Hierarchical linear modeling analyses indicated there was substantial within-person variance in CSE over time and this variability was related to income and education. These findings shed additional light on the fundamental nature of CSE, contributing to a new perspective on this construct with potential implications for employees, organizations, and researchers.