Background æThe value of siblings for social-emotional, cognitive, behavioral and overall psychological well-being has been well-documented. The purpose of this presentation is to examine whether having a sibling impacts the core developmental domains in early childhood. æMethods æThe data for this study was obtained through Project Play. æData collection included: (1) the administration of the Battelle Developmental Inventory Screening Test (second edition: BDI-2 ST), which is a standardized, norm-referenced measure of a childÍs development across five domains; and (2) a Child and Family Background Form, in which information regarding siblings in the household was obtained. æFirst, subjects, ranging in age from 8 to 60 months, will be identified as having siblings. æNext, subjects identified as being only children will be selected to match for age. The scores on the five subdomains of the BDI-2 ST for both groups (adaptive, cognitive, motor, personal-social, and self-help) will be compared. æææHypotheses æBased on the findings reported in previous literature, we expect having a sibling to have the largest impact in the domain of personal-social skills so that children with siblings will have higher scores in the BDI-2 ST personal-social domain than children without siblings. We expect a similar trend for the BDI-2 ST cognitive domain based on the literature base so that children with siblings will have higher score in the cognitive domain than children without siblings. ææImplications æInformation regarding the way in which siblings impact development will lead to a greater understanding of the influence of family structure on early childhood development.