This is the first report from the third wave of the Early Childhood Longitudinal Study, Birth Cohort (ECLS-B), a study of a nationally representative sample of children born in 2001. The report provides descriptive information about these children when they were about 4 years old. It also includes results from language, literacy, mathematics, and fine motor skills assessments, and information on children's nonparental education and care experiences. For example, the report shows that 65 percent of children between 48 and 57 months of age were proficient in number and shape recognition, a component of the mathematics assessment. Proficiency varied by several child and family characteristics such as socioeconomic status. Forty percent of children from low SES families were proficient compared to 87 percent of children from high SES families. For experiences with nonparental care and education settings, the report shows that approximately 20 percent of the cohort did not regularly attend such settings. The primary nonparental care and education setting was a non-Head Start center for 45 percent of the cohort, a Head Start center for approximately 13 percent of the cohort, a home-based relative setting for 13 percent of the cohort, and a home-based non-relative setting for 8 percent of the cohort.