Gottfredson and Hirschi's (1990) A General Theory of Crime has sparked a great deal of theoretical debate and empirical investigation. Tests of the theory have focused on measuring the core element, the latent trait of self-control. The majority of this research has used the 24-item scale developed by Grasmick et al. (1993), and a great deal of attention has been directed at the validity of this scale. Empirical debate revolves around the unidimensionality of the scale as established using conventional factor analytic techniques [exploratory factor analysis (EFA) and confirmatory factor analysis (CFA)]. This article provides the first application of an item response theory (IRT) Rasch model to the validation of the Grasmick et al. scale. IRT models focus on the interaction between the human subject and survey items and the extent to which cumulative scales fail to provide fundamental measurement. Although conventional factor analyses yield results similar to those previously reported, IRT analysis revealed that one's level of self-control influences self-report responses, a finding consistent with Hirschi and Gottfredson. Notes, tables, figures, references