Objective: The purpose of the study was to define the latent structure of parent-reported manic symptoms and their association with functional impairment and familial risk in a community sample of Brazilian children. Method: We screened for manic symptoms in a community sample of 2,512 children 6 to 12 years of age. Parents of children with ‘episodes of going abnormally high’ completed a detailed mania section (n = 479; 19.1%). Confirmatory factor analysis (CFA) tested a solution with ‘Under-Control (UC)’ and ‘Exuberant (EX)’ dimensions, investigating the severity (threshold) and factor loading of each symptom. We also used latent class analysis (LCA) to evaluate the latent categorical structure of manic symptoms. Associations of these latent constructs with psychiatric comorbidity, psychosocial impairment, and family history of psychopathology were tested. Results: The 2-dimensional model fit the data well. Only the UC dimension was associated with psychiatric morbidity, psychosocial impairment, and a family history of mania, depression, or suicide attempts. Both UC and EX items discriminated subjects with ‘episodes of going abnormally high,’ but EX items lay at the mild end of the severity spectrum, whereas UC items lay at the severe end. The LCA yielded a small group of children with high levels of manic symptoms and a distinct profile of psychiatric comorbidity and impairment (‘high-symptom group’). Conclusion: In a large, community-based sample, we found a 2-dimensional latent structure for parent-reported manic symptoms in youth, and demonstrated familial associations between the UC dimension and affective disorders. Both UC and EX items are clinically useful, but their contributions vary with symptom severity.