The goal was to examine whether children who screen positive for social-emotional/behavioral problems at 12 to 36 months of age are at elevated risk for social-emotional/behavioral problems in early elementary school. The sample studied (N = 1004) comprised an ethnically (33.3% minority) and socioeconomically (17.8% living in poverty and 11.3% living in borderline poverty) diverse, healthy, birth cohort from a metropolitan region of the northeastern United States. When children were 12 to 36 months of age (mean age: 23.8 months; SD: 7.1 months), parents completed the Brief Infant-Toddler Social and Emotional Assessment and questions concerning their level of worry about their child's behavior, emotions, and social development. When children were in early elementary school (mean age: 6.0 years; SD: 0.4 years), parents completed the Child Behavior Checklist and teachers completed the Teacher Report Form regarding behavioral problems. In a subsample (n = 389), parents reported child psychiatric status. Brief Infant-Toddler Social and Emotional Assessment screen status and parental worry were associated significantly with school-age symptoms and psychiatric disorders. In multivariate analyses that included Brief Infant-Toddler Social and Emotional Assessment status and parental worry, Brief Infant-Toddler Social and Emotional Assessment scores significantly predicted all school-age problems, whereas worry predicted only parent reports with the Child Behavior Checklist. Children with of-concern scores on the problem scale of the Brief Infant-Toddler Social and Emotional Assessment were at increased risk for parent-reported subclinical/clinical levels of problems and for psychiatric disorders. Low competence scores predicted later teacher-reported subclinical/clinical problems and parent-reported disorders. Worry predicted parent-reported subclinical/clinical problems. Moreover, the Brief Infant-Toddler Social and Emotional Assessment identified 49.0% of children who exhibited subclinical/clinical symptoms according to teachers and 67.9% of children who later met the criteria for a psychiatric disorder. Screening with a standardized tool in early childhood has the potential to identify the majority of children who exhibit significant emotional/behavioral problems in early elementary school.