The influence of birth order, language background, socioeconomic status, sex of the infant, and caregiver-infant interaction on the developmental competence of 106 preterm infants was assessed at 4, 9, 18, 24, and 25 months of age. The results showed that developmental scores were predominantly influenced by the infant's ordinal position in the family and the nature of the caregiver-infant interactions until 2 years of age. Thus, the influence of preterm birth is modulated by these factors and sociocultural variables in the succeeding months. Differences between infants from varying socioeconomic groups and language background did not emerge until 24 months. The clinical implication is that intervention which affects the nature of the caregiver-infant interaction may indirectly improve the child's development and may prevent some of the cognitive disabilities often associated with preterm birth.