This short-term longitudinal study investigated the effectiveness of an infant-based, family-focused intervention at birth, on patterns of mother-infant interactions, as well as on mothers' representations of their newborns and of themselves, four months after birth. The effectiveness of the Clinical Neonatal Behavioral Assessment Scale (CLNBAS) (Nugent & Brazelton, 2000a), a new clinical adaptation of the Neonatal Behavioral Assessment Scale (NBAS) (Brazelton, 1973, 1984; Brazelton and Nugent, 1995), as a means of positively influencing the mother-infant relationship was examined. The objectives of this study were to determine the effectiveness of the CLNBAS intervention on mother-infant interaction, specifically, mothers' sensitive caring, and infants' cooperative responding, as measured by the CARE-Index (Crittenden 1981, 1988, 1998), and on mothers' representations of their babies, and their representation of themselves as mothers, as measured by the Maternal Representations Questionnaire (MRQ (Stern-Bruschwieler & Stern, 1998). This was the first controlled study using the CLNBAS. Results of the CARE-Index scoring of mother-infant play showed positive trends in mothers' sensitivity and babies' cooperativeness were associated with the CLNBAS intervention. A significant, strong relationship existed between mothers' sensitivity and babies' cooperativeness. An odds ration (OR) analysis was performed with CARE-Index scores. Receiving the intervention more than doubled the chance of a mother being sensitive, and it increased the chance of a baby being cooperative by approximately four times, which was significant. MRQ results showed mothers' scores of their representations of their babies and of themselves tended to be positive, and there was a general growth in this positiveness over the course of the study for both experimental and control mothers. The total range of MRQ scores was narrow across the three data collection periods. Correlations between mothers' MRQ scores of their babies and of themselves over the three time periods showed some significant though modest relationships. There were no significant differences in MRQ scores associated with the CLNBAS intervention. In sum, this study has shown the CLNBAS intervention to be effective in facilitating mothers' sensitivity with their babies, and babies' cooperativeness with their mothers.