This short term longitudinal study of parent-infant interactions over 4 months beginning at birth examines interrelations among patterns of interactive behavior, characteristics of the parents and infants, and parental attitudes, knowledge and feelings in relation to their infants. Forty sets of mothers and fathers were observed interacting with their infants in a feeding and play context in the newborn period in a hospital setting, at three weeks and at three months in a home setting. A 45 item questionnaire was completed by each parent at each time point. Results showed that: (1) both parents and infants regulate each other's behavior beginning as early as the newborn period; (2) fathers are active participants in interaction with their infants over the first several months of infant life; (3) early social interaction is better understood when parents are affirmed as cognitive organisms and are assessed for their attitudes and attributions about infants; (4) sex of the infant is a determinant of early parent-infant interaction; (5) parent behavior in the triadic family context clearly modifies the interaction patterns of both mothers and fathers. (SE)