The authors empirically examined two operationalizations of the core self-evaluation construct: (a) the Judge, Erez, Bono, and Thoresen 12-item scale and (b) a composite measure of self-esteem, self-efficacy, locus of control, and neuroticism.The study found that the composite scale relates more strongly than the shorter scale to performance, perceived job complexity, positive affectivity, personal trust, and belief in a just world. However, the short scale performed well and may be more practical in organizational research. The authors conclude that the 12-item measure is better used in research when participant time is limited and that a composite index is better when time is not a constraining factor in the data-collection process. (Contains 3 tables.)