In this paper, we report new data on mutual olfactory recognition between mother and child. Newborn infants were filmed since birth. When awakening in the mother's room at the Clinical Hospital, they were confronted with a cotton pad impregnated with diverse secretions of the mother and a cotton pad impregnated with the same secretions of another mother or a pad with no specific odour. We used a double-blind technique. By analyzing the films, frame by frame, we found that the whole area swept by the nose and the arms was significantly decreased in the child whose nose came into contact with the "mother" pad. The method could be used to study other sensory abilities in the baby. The olfactory abilities of the mother in relation to the baby were also tested with the double-blind principle. We found (i) on the 3rd and 4th days after birth, most mothers recognized the baby's odour, (ii) this faculty decreased from the 4th to the 6th day, and finally (iii) increased from the 8th day. These results are discussed. We also found that one-third of 3 to 5 years old children more often chose a tee-shirt worn against the mother's skin for 2 to 3 days than any other tee-shirt (worn by an alien mother or with no specific odour). It appears that olfactory cues can play a role in the attachment of the baby to its mother, and that they still are involved in that process when the child is between 3 and 5 years old.