Twenty-four clients were asked to nominate an incident that was critical to the development of their therapeutic relationship with a trainee therapist. Therapist interventions within each client relationship building incident (RBI) were identified. The results of multiple regression indicated that attachment anxiety moderated the relationship between attachment avoidance and type of therapist interventions present in the RBI. Secure clients (low anxiety, low avoidance) nominated incidents with higher levels of exploratory interventions. Dismissing clients (low anxiety, high avoidance) nominated incidents with higher levels of supportive interventions. Issues related to tailoring therapist behaviours to client attachment style to facilitate positive alliances are discussed. (Contains 3 tables and 1 figure.)