This report provides an account of the nature and purposes of data collected concerning the health, nutrition, and physical development of infants during the first three years of life, in order to compare the physical health of children in family or group day care and children with no previous day care experience. The data collected include the infants's birth history; detailed physical examinations of children at 6, 12, 18, and 36 months; laboratory blood tests; vision, hearing, and dental screening procedures; and interim reports from outside agencies. The factors under analysis include growth and development, the presence or absence of major and/or minor abnormalities, and the day care center's effect on children's physical development. No study conclusions have yet been reached. (ED)