Children from 10 sites in the United States were followed from birth to age 3 to determine how experiences in child care relate to cognitive and language development (Ns varied between 595 and 856, depending on the assessment). Multiple assessments of family and child care environments and of cognitive and language competence were collected. Analyses that adjusted for maternal vocabulary score, family income, child gender, observed quality of the home environment, and observed maternal cognitive stimulation indicated that the overall quality of child care, and language stimulation in particular, was consistently but modestly related to cognitive and language outcomes at ages 15, 24, and 36 months. The effect sizes for high (top quartile) versus low (bottom quartile) quality ranged from .18 to .48. After adjusting for child care quality, cumulative experience in center-based care was associated with better outcomes than was participation in other types of care. The amount of time children spent in care was not related to outcomes. Children in exclusive maternal care did not differ systematically from children in child care. Tests for lagged relations of earlier child care experiences to later performance (adjusting for current child care) showed that language stimulation predicted subsequent cognitive and language performance 9 to 12 months later. Although children in center care at age 3 performed better than children in other types of care, earlier experience in child care homes was associated with better performance at age 3 than was experience in other types of care. The relations of child care variables to outcomes did not vary consistently as a function of family income, quality of home environment, child gender, or ethnic group.