Disruptive behavior disorders (DBDs), including Oppositional Defiant Disorder (ODD) and Conduct Disorder (CD), are among the best, empirically documented forms of early childhood psychopathology. Recent studies have demonstrated that DBDs are identifiable in early childhood, while also highlighting the limitations of current DBD nosology for identifying preschool disruptive behavior in a developmentally sensitive and specific manner. Limitations include: (1) overlap of many ODD symptoms with normative misbehaviors; (2) developmental inappropriateness of the majority of CD symptoms; and, (3) failure to capture substantial clinical heterogeneity across the broad group of children with DBDs. The proposed study is designed to help establish more precise parameters for identifying and classifying disruptive behavior in preschool children and to distinguish it from normal variation by using a rigorous developmentally-sensitive, multidimensional approach. Specifically, we propose to assess preschool disruptive behavior within the following multidimensional framework: a central Shared Disruptive Behavior Severity Dimension and four specific behavioral dimensions representing distinct facets of disruptive behavior: (1) Temper Loss; (2) Noncompliance; (3) Aggression and, (4) Lack of Concern for Others. Two general population samples from pediatric clinics will be recruited: (1) a Calibration Sample (N=1,500) and, (2) an independent Replication Sample (N=2,200). These pediatric samples will be stratified by child age, sex, ethnicity and poverty status. A Validation Sub-Sample (N=350), enriched for disruptive behavior, will be drawn from the Replication Sample, with intensive laboratory assessment at baseline and a 6-month follow-up. Specific aims of the proposed study are to: (I) Document the distributional characteristics of temper loss, noncompliance, aggression and lack of concern for others in a normative preschool sample. (II) Empirically test the developmentally-sensitive, multidimensional approach to preschool disruptive behavior by (a) calibrating the multidimensional model using bi-factor Item Response Theory (IRT), including comparison of the fit of the 4-dimension model to alternative models; (b) testing the fit of the model across demographic sub-groups and children with- and without co- occurring psychopathology; (c) replication in an independent sample and; (d) deriving disruptive behavior sub- types based on cross-dimension patterns. (III) Demonstrate the construct, criterion, convergent, divergent and incremental validity of the developmentally-sensitive, multidimensional approach. In particular, establish its (a) association to key child and family markers of DBD risk; (b) capacity to discriminate preschoolers with impairment over time and; (c) incremental utility for prediction beyond DSM-IV DBD diagnoses and; (IV) Demonstrate the validity of the four specific dimensions by testing for hypothesized differentiated associations to directly assessed features of child disruptive behavior and neurocognitive functioning. Precise characterization of the phenomenology of preschool disruptive behavior is vital for identifying distinct etiological substrates, predicting meaningful variation in course and, enhancing intervention effectiveness.