Objective: Investigating dimensions of oppositional symptoms may help to explain heterogeneity of etiology and outcomes for mental disorders across development and provide further empirical justification for the "DSM-5"-proposed modifications of oppositional defiant disorder (ODD). However, dimensions of oppositionality have not previously been tested in samples outside Europe or the United States. In this study, we used a large Brazilian community sample to compare the fit of different models for dimensions of oppositional symptoms; to examine the association of psychiatric diagnoses and symptoms with dimensions of oppositionality; and to examine the associations between dimensions of oppositionality and parental history of mental disorders. Method: A Brazilian community sample of 2,512 children 6 through 12 years old were investigated in this study. Confirmatory factorial analyses were performed to compare the fit of alternative models, followed by linear and logistic regression analyses of associations with psychiatric diagnosis and parental history of psychopathology. Results: A three-factor model with irritable, headstrong, and hurtful dimensions fitted best. The irritable dimension showed a strong association with emotional disorders in the child (p less than 0.001) and history of depression (p less than 0.01) and suicidality (p less than 0.05) in the mother. The headstrong dimension was uniquely associated with attention-deficit/hyperactivity disorder (ADHD) in the child (p less than 0.001) and with maternal history of ADHD symptoms (p less than 0.05). The hurtful dimension was specifically associated with conduct disorder (p less than 0.05). Conclusions: Our findings from a large community sample of Brazilian children support a distinction between dimensions of oppositionality consistent with current "DSM-5" recommendations and provide further evidence for etiological distinctions between these dimensions. (Contains 1 figure and 5 tables.)