Infants' differential vocal response (DVR) towards their mother and a female stranger at 3 months of age has been predominantly investigated as an index of early cognitive functioning. The present study explored the relationship between DVR and different infant and mother indicators of the developing relationship quality in a sample of 23 mother-infant dyads. Mother-infant interactions and stranger-infant interactions were videotaped during home visits when the infants were 3 months old. At the age of 12 months, infants' behaviour was assessed in the Ainsworth's strange situation. In both assessments, mothers noted the infants' behavioural states on 3 successive days. Results revealed a specific relation between DVR and the emotional atmosphere of the early mother-infant interaction. Particularly, DVR was less pronounced in favour of the mother when the mother displayed emotional expressions defined as rejection. DVR is discussed as an index that may indicate both infant emotional engagement and infant cognitive competencies. (Contains 5 tables.)