The Early Childhood Longitudinal Study, Birth Cohort (ECLS-B), is a study that is part of the Early Childhood Longitudinal Study program; program data is available since 1998-99 at https://nces.ed.gov/ecls/dataproducts.asp. ECLS-B (https://nces.ed.gov/ecls/birth.asp) is a longitudinal study that is designed to provide policy makers, researchers, child care providers, teachers, and parents with detailed information about children's early life experiences. The study was conducted using multiple data collection methods (computer-assisted in-person interviews, computer-assisted telephone interviews, self-administered questionnaires, and direct observation) to collect information about children's characteristics, behaviors, development, and experiences from the adults who were important in the children's lives, including mothers, fathers, early care and education providers, and teachers. Direct child assessments were used to measure children's development, knowledge, and skills from the time the children were about 9 months old. A nationally representative sample of approximately 14,000 children born in the U.S. in 2001 was fielded. Key statistics produced from ECLS-B focus on children's health, development, care, and education during the formative years from birth through kindergarten entry.