This chapter will review comparative treatment studies before going on to consider similarities and differences between behavioural and psychodynamic approaches. A final section will summarise the issues and findings. Controlled comparative treatment studies with randomly allocated treatment groups are difficult to justify on ethical grounds. Clinical work is extremely time-consuming and long-term follow-ups pose another time burden on the therapist researcher. Under the circumstances, it is perhaps not surprising that there have been relatively few large scale treatment studies, hardly any comparative investigations and only two studies that have included a control group (Waldfogel, Tessman and Hahn, 1959; Miller, Barrett, Hampe and Noble, 1972).