A 42-year-old married female client enters the therapist's office and describes herself as having a "phobia of leaving the house." She states that she has had various fears since shortly after she was married 20 years ago, but that these feelings of anxiety surrounding leaving her home have become so intense that she has rarely left the house in the last 3 years. How does the therapist go about determining the appropriate treatment for this client? Certainly most therapists would agree that further information-gathering about the woman's situation is necessary. But how does one go about assessment in a systematic manner so that the information obtained can lead to treatment decisions? In the current stage of the development of psychotherapy, the crucial work of selecting a treatment for a particular client is, unfortunately, frequently based on a combination of one of two factors: the diagnostic category into which the client's symptoms fall, and the theoretical predilections of the therapist. Thus, many therapists would diagnose this woman's problems as "agoraphobia," and, depending on their theoretical affiliation, they would select a treatment popularly acknowledged (within their affiliation group) to be effective with "agoraphobia."