The relationship between aspects of mother-infant interactional behavior (vocalization, smiles, mutual eye contact, and facing position) and the infant's developmental level was investigated through both observation and intervention efforts. A sample of 33 primiparous mothers (mean CA of 22 years) from low income families and their infants (mean CA of 8 months) were videotaped during interactions with each other. Analysis showed that maternal position during interaction (facing, partially facing, or behind the infant) was strongly related to the frequency of maternal interactional behavior and indices of infant language and cognitive development. Intervention to teach mothers to use the facing position showed that change in position was related to increases in both maternal interactional behavior and infant development. The intervention involved use of the videotapes, informal discussion and role play activity. The results were considered relevant for intervention with infants at risk for developmental delay, abuse, and neglect. (Author/SS)