OBJECTIVES: To describe the demographic and clinical characteristics of pediatric multiple sclerosis (MS) in the United States. METHODS: This prospective observational study included children and adolescents with MS. Cases were evaluated across 9 geographically diverse sites as part of the US Network of Pediatric MS Centers. RESULTS: A total of 490 children and adolescents (324 girls, 166 boys) were enrolled; 28% developed symptoms before 12 years of age. The proportion of girls increased with age from 58% (<12 years) to 70% (≥12 years). Race and ethnicity as self-identified were: white, 67%; African American, 21%; and non-Hispanic, 70%. Most (94%) of the cases were born in the United States, and 39% had 1 or both foreign-born parents. Fifty-five percent of cases had a monofocal presentation; 31% had a prodrome (most frequently infectious), most often among those aged <12 years (P < .001). Children aged <12 years presented more commonly with encephalopathy and coordination problems (P < .001). Sensory symptoms were more frequently reported by older children (ie, those aged =12 years) (P < .001); 78% of girls had MS onset postmenarche. The initial Expanded Disability Status Scale score for the group was <3.0, and the annualized relapse rate was 0.647 for the first 2 years. Interval from symptom onset to diagnosis and from diagnosis to initiation of disease-modifying therapy was longer among those <12 years of age. CONCLUSIONS: Pediatric MS in the United States is characterized by racial and ethnic diversity, a high proportion of children with foreign-born parents, and differences in clinical features and timing of treatment among those <12 years of age compared with older children.