Objective: There is increasing emphasis on dimensional conceptualizations of psychopathology, but empirical evidence of their utility is just emerging. In particular, although a range of multidimensional models have been proposed, the relative fit of competing models has rarely been tested. Furthermore, developmental considerations have received scant attention. In this study, we tested a developmentally based, four-dimensional model of disruptive behavior theorized to represent the defining features of disruptive behavior at preschool age: Temper Loss, Noncompliance, Aggression, and Low Concern for Others. Method: Model testing was conducted in two independent samples of preschoolers: Clinically Enriched Sample (n = 336) and Epidemiologic Sample (n = 532). The tau-equivalent confirmatory factor analyses were used to test the fit of the Developmental Model relative to three leading competing models ("DSM" oppositional defiant disorder (ODD)/conduct disorder (CD) Model, "Callous" Model, and an "Irritable/Headstrong/Hurtful" Model). Reliability of the four dimensions was also tested. Validity of the dimensions was tested by predicting multi-informant, multi-method ratings of disruptive behavior and impairment, and incremental utility relative to "DSM" symptoms. Results: In both samples, the Developmental Model demonstrated a superior fit compared with the competing models within the full sample, and across key demographic subgroups. Validity was also demonstrated, including incremental utility relative to "DSM-IV" disruptive behavior symptoms. Conclusions: Critical next steps for achieving scientific consensus about the optimal dimensional model of disruptive behavior and its clinical application are discussed. (Contains 8 tables and 1 figure.)