The efficacy of developmental intervention in the neonatal intensive care unit for mothers of preterm infants with low socioeconomic status was evaluated. Mothers were assigned to an experimental group in which they met at least weekly with an infant-development specialist or to a control group in which they did not. During the sessions, they participated in a structured developmental and behavioral assessment of their infants, with the goal of enhancing their ability to provide appropriate interactions and environmental stimulation for their infants. When the infants were 4 and 8 months of age, follow-up home visits by a nurse who was unaware of group assignment showed that the experimental-group infants performed more optimally on the Bayley Mental scale (Bayley Scales of Infant Development) at 4 and 8 months of age and on the Bayley Motor scale at 4 months. In addition, the home environment was more developmentally appropriate at 4 months of age, and the mothers rated their babies as temperamentally less difficult at 4 and 8 months. We conclude that a mother-focused, neonatal intensive care unit-based program that utilizes the assessment process in a therapeutic way is an effective strategy in the initiation of interventions for families of low socioeconomic status whose infants were born prematurely.