In this chapter, we will explore the reasons for carrying out a comprehensive assessment before deciding on the appropriate intervention. We will then consider how this might be achieved. The whole approach is person centred, attempting to engage with the individual and their surroundings, to work out how they see the world and what would make it both better, and have the potential for further improvement. This is a very dynamic approach which facilitates growth. This must be detailed for people who are responding to traumatic events in childhood. This chapter addresses the assessment of the individual. For an intervention for a traumatised person, there will be systemic issues to assess and plan for, and sometimes the trauma in others, for example parents.