37 mother-preterm and 42 mother-full-term infant pairs were assessed at 1, 4, 8, and 12 months following hospital discharge. The psychosocial functioning of the families was assessed at 1 and 8 months by interview, infants received developmental assessments at 4 and 12 months, and mother-infant interactions were observed in unstructured and semistructured situations at 4, 8, and 12 months. Significant differences were found in both mothers' and preterm infants' interactive behavior across the first year of life, extending the findings of previous research that had noted differences during early infancy. Additionally, preterms performed significantly below full-terms on measures of cognitive and language development corrected for gestational age. Results are discussed in terms of the persistence of interactive differences in mother-preterm pairs and the possible effects on their relationship and infant developmental outcome.