The diagnostic and treatment procedure considered in the present and subsequent chapters represents a detailed look at the rapid behavioural treatment approach reported previously in Blagg (1977, 1979 and 1981) and successfully utilised in Blagg and Yule’s (1984) comparative treatment study. Whereas previous accounts dwelt upon pragmatic and content issues this present account will also include a careful review of process issues. This chapter will explore the issues and procedures involved in gathering relevant data whilst Chapter 7 will focus on treatment and resistance to treatment. Finally, Chapter 8 provides a series of illustrative case studies.