A clinical intervention based on behavioral items from the Brazelton Neonatal Behavioral Assessment Scale (BNBAS) was implemented at a hospital among 40 lower middle class Portuguese mothers between 18 and 35 years old 3 days after delivery. The intervention aimed to promote mother-infant attachment by increasing mothers' awareness of the individual social competencies of their newborn and mothers' proficiency in interacting with infants. Infants were observed for about 30 minutes and assessed with the BNBAS on the 3rd and 28th day of life. Mothers assigned to the experimental group were visited by a pediatrician who demonstrated BNBAS items of animated visual and auditory sensorial orientation, consolability, and cuddliness. On an individual basis, mothers were invited to elicit auditory performances of infants, and talk to, console, and hold them. Mother-pediatrician dialogue focused on infants' observed competencies and behaviors. A control group of 20 mothers received instruction on special pediatric care they should provide. Two instruments were used twice to measure changes in mothers' attitudes and expectations, and one was used to assess mothers' perceptions of their babies. Videotaped behavioral interactional sequences were analyzed with Lieberman's Observation Scale to determine to what extent dyads had achieved homeostasis and attachment. Findings suggested that the early intervention led to positive changes in maternal and infant behavior. (RH)