The Infant Health and Development Program (IHDP) is an intervention aimed at improving the health and development of premature, low birth-weight infants through a combination of education and support for parents plus enriched educational day care and health services for children. A randomized clinical trial procedure was used at eight program sites to example the impact of IHDP on children?s growth and development from birth to age 3. Follow-up assessments were conducted at ages 5 and 8. The effect of the program on children?s intelligence at age 3 was greater for those children from low-quality home environments. However, the home environment was not a moderator of program impact on children?s intelligence at the later assessment points, nor was it a moderator of program impact on children?s behavior.