This article reports on the preliminary outcomes from a major longitudinal study of the influences of non parental child care, experienced during the first year of life, on the developmental progress of the children involved. The study is sponsored by the US National Institutes of Child Health and Development (NICHD) Study of Early Child Care. A major focus of the study is on ascertaining under what conditions children thrive in child care and under what conditions their development is compromised. Another central issue is the determination of the processes by which child care and the family environments affect children's development.