More than 485,000 low-birth-weight, premature babies are born in the U.S. each year. The increase in preterm births since 1990 may be due to assisted pregnancies and births to older mothers. Although their survival rates are improving, many premature infants experience long-lasting developmental and behavioral problems. The author describes recent findings on the impact of the physical environment of the Neonatal Intensive Care Unit (NICU) on the behavioral and physiological development of preterm infants and the importance of establishing responsive caregiving relationships. Individualized, relationship-based developmental intervention in the NICU should focus not only on medical and nursing care, but also on safety, privacy, confidentiality, comfort, and togetherness for the whole family.