This study examined the implementation of a model of managing aggressive and harmful behaviour in an adolescent in-patient psychiatric unit. This model, Positive Behaviour Management, replaced a previous model, Control and Restraint, which was considered unsuitable. Both models included the use of physical interventions, and the research into such techniques is considered. The aims of the study were to evaluate the effects of three training courses on staff confidence in managing aggressive behaviour, knowledge about good practice and staff satisfaction with the new model. A multiple baseline design was used to examine change before, during and after the training period, and at one-year follow-up. The study found that staff confidence increased significantly following training but had returned to baseline levels by the time of follow-up. Staff knowledge significantly increased during the study periods but did not appear to be directly linked to the training courses, and was maintained at one-year follow-up. Staff reported significantly higher levels of satisfaction with the new model Steve Killick is with the Harvey Jones Adolescent Unit, a Tier Four CAMH Service covering the geographical area of South Wales. The unit offers a variety of therapeutic approaches including systemic family therapy, cognitive behaviour therapy and psychotherapy within a therapeutic milieu, and works with young people aged between 11 and 18 who are experiencing severe mental health problems, disorders and illness. Prof. David Allen is Consultant Clinical Psychologist & Head of Specialist Services with the Bro Morgannwg NHS Trust, providing specialist services for people with intellectual disabilities comprising a range of intensive community behavioural intervention teams, acute assessment and intervention units, and domestic-scale, community-based long-stay continuing care facilities. Positive behavioural support is the prevailing therapeutic model within the service; the service provides extensive training to external agencies in these approaches and in the safe management of aggressive and other challenging behaviours.than with the previous model, which were maintained at follow-up. The findings of the study and the difficulties encountered are discussed in relation to similar findings elsewhere.