The aim of this chapter is to explore how mental health organisations could use guidelines within their services. Our experience has mainly been in specialist mental health trusts, which is why we have focused on these within the chapter. However, mental health guidelines could be used in any organisation providing mental healthcare, from general primary care settings to multidisciplinary interface services, including services integrated with social care. We believe that the principles we highlight for specialist mental health trusts apply equally to other mental health services settings.