353 Hypochondriasis is presently classified as a somatoform disorder. However, in terms of phenomenology and cognitive processes, it is probably best considered as a form of severe and persistent anxiety focused on health. This reconceptualization allows the application of Beck's general cognitive theory of anxiety (1985) to the understanding and treatment of hypochondriasis. In this paper, the classification and phenomenology of health anxiety is explained in terms of a specific cognitive-behavioral conceptualization. The way this conceptualization has been successfully applied to the treatment of health anxiety and hypochodriasis is described. The all-important task of engagement is accomplished as part of the cognitive assessment, which helps the patient develop and evaluate an alternative understanding of their problems. This understanding focuses on how misinterpretations of health-related information (mainly bodily variations and medical information) leads to a pattern of responses including anxiety, distorted patterns of attention, safety-seeking behaviors, and physiological arousal. These responses in turn account for the patient's pattern of symptoms and functional impairment. Treatment progresses by helping the patient actively explore the validity of the alternative account of their problems arising from the shared understanding. This objective is accomplished through two avenues: one, discussion, which has the purpose of making sense of the person's experience; and two, active evaluation of the mechanisms involved, through collaboratively designed and implemented behavioral experiments. Evidence from randomized controlled trials strongly suggests that cognitive treatments are effective and that the effects are specific to the treatment techniques used. Development of this work will likely branch into medical problems, where a prominent component of health anxiety exists. [Brief Treatment and Crisis Intervention 3:353–367 (2003)] KEY WORDS: hypochondriasis, somatoform disorders, cognitive behavioral therapy. Until relatively recently, the treatment of hy-pochondriasis was not considered to be an im-portant issue, as this condition was regarded as invariably being secondary to depression or anxiety. Kenyon's (1964) influential study of pa-tients with hypochondriacal beliefs suggested that hypochondriasis is always secondary to an-other primary disorder, usually depression. It was subsequently suggested that hypochondri-acal beliefs occurring in the absence of affective symptoms were due to "masked depression." More recently, studies have convincingly identi-fied a primary disorder in which false concerns about health are the central problem, to which affective symptoms are secondary (Bianchi, 1971). The paper by Barsky and Klerman (1983) marked the reestablishment of hypochondriasis not only as a recognizable clinical condition but also as an important research topic (e.g., As-mundsen & Cox, 2001). Primary hypochondri-asis is now included in both ICD 10 (World Health Organization) and DSM-IV (APA, 1994). Although hypochondriasis is now accepted as a primary problem, its taxonomy remains controversial. Debate continues as to whether it is best seen as a somatoform disorder (as presently classified) or as an anxiety disorder (Salkovskis & Warwick, 1986; Warwick & Sal-kovskis, 1990). To place this debate in con-text, let us examine the diagnostic criteria presently used. According to DSM-IV, hypo-chondriasis is characterized by preoccupa-tion with fears of having, or the idea that one has, a serious disease, based on the person's misinterpretation of bodily symptoms. Thus, the problem is characterized as a cognitive one, involving erroneous appraisals. Note that this definition bears a strong resemblance to the cognitive theory of panic disorder (Clark, 1986; Salkovskis, 1989). The definition requires that the preoccupation persist despite appropriate medical evaluation and reassurance, meaning that the failure of a psychological intervention (reassurance) by a doctor is required for the di-agnosis to be made. In addition, formal diagno-sis dictates that the preoccupation has to cause clinically significant distress or impairment in social, occupational, or other important areas of functioning. Despite the considerable health care resources utilized by people with hypochondriasis, nei-ther physical medicine nor psychiatry has pre-viously established an effective treatment. Hypochondriasis has long been regarded as an intractable disorder, with supportive therapy and reassurance the best that can be offered. To some extent it has at times also been seen as a nuisance, with some considering it to be akin to factitious problems and malingering. Recently, well-defined cognitive-behavioral theories of hypochondriasis have been de-scribed, and treatment strategies derived from them have been empirically tested in random-ized controlled trials. The evidence from this re-search strongly suggests that this approach is effective both in engaging these patients in treatment and ameliorating the clinical symp-toms. The cognitive-behavioral theory of hypochondriasis provides a comprehensive ac-count of the psychological processes involved in the disorder, including etiological and main-taining factors. Modification of the important psychological factors involved in the mainte-nance of each case should lead to a resolution of the central problem—that is, a false belief that the patient is physically ill, based on the misin-terpretation of innocuous physical symptoms or signs, and based on health-related information from professionals, the media, and the Internet.