This article focuses on how in the past 10 years, research on physical abuse and problems displayed by children under the age of six has contributed to the issue of attachment. A longitudinal study of a group of children born to teenage mothers found that the mother-child bond is linked to the antisocial behaviour of girls but not of boys. A project was undertaken to explore the role of father-child conflict in externalized aggressive behaviour in children, particularly in boys. As a result, the theory of activated attachment behaviour was formulated in order to better understand the influence of the father on child attachment and development. The article concludes by underlining the importance now given to the issue of attachment by the Centre jeunesse de Montréal-Institut universitaire in the treatment of children.