Using attachment theory as a theoretical framework, the concept of the attachment dynamic is introduced as a model to explain (1) how individual members of a family behave as though they constituted a system (2) the extent to which the complementary activitiesof attachment andcare-giving behaviour (a) govern the movements of family members towards or away from each other; (b) affect the degree to which they each engage in creative exploratory activities: and (c) influence the internal representation each family member builds of him or herself in action with others or acting alone. The attachment dynamic is considered to be played out in many forms which range along a continuum from highly adaptive to grossly maladaptive. The characteristics of effective care-giving behaviour, adaptive attachment behaviour and exploratory behaviour, integrated within adaptive forms of the attachment dynamic, are contrasted with ineffective care-giving, continuing unassuaged attachment behaviour and anxious, frustrated or inhibited exploratory behaviour which are found in maladaptive forms of the dynamic. The implications of this model for family therapy are outlined.