attack come on. This avoidance may be relatively subtle-for example, the man with panic disorder who gives up running because his rapid heartbeat makes him feel like he is panicking or having a heart attack. Or it may be highly obvious-for example, the woman who becomes afraid to leave her home unless she is accompanied by a trusted person who will take care of her should she panic. When avoidance is significant, the person is said to have panic disorder with agoraphobia, for which the lifetime prevalence is about 1% (Kessler et al., 2006). Another 1% will have agoraphobia with panic attacks but will not meet full diagnostic criteria for panic disorder (Kessler et al., 2006); for example, they will not have had recurrent unexpected panic attacks. Much of the literature cited in this chapter was written before diagnostic distinctions between agoraphobia with and without panic disorder were made, and phenomenologically there is little difference to the patient between these disorders. I use the term agoraphobia to refer to both groups. Moreover, some more recent studies have focused on panic disorder without reference to whether there is associated agoraphobia. Thus, it is not always be possible to make distinctions between panic disorder with and without agoraphobia. When possible, I do so.The social and health consequences of panic disorder are great. According to epidemiologic research, these include increased risk of alcohol and drug abuse, mood disorders, other anxiety disorders, subjectively poor health, poor social functioning, high use of health care services and emergency rooms, and financial dependence on disability and welfare payments (Kessler et al., 2006;Markowitz, Weissman, Ouellette, Lish, & Klerman, 1989). Disability is greatest for those who develop agoraphobia as a complication of panic disorder (Kessler et al., 2006). The more disabled patients become, the more likely they are to rely on family members for their daily functioning, posing a heavy burden on their intimate others. Reflecting not only agoraphobic patients' restricted lives but also the preponderance of women with the disorder-as many as 80% in clinical samples (Chambless & Mason, 1986)-an early synonym for agoraphobia was housebound housewives. Epidemiologic research has suggested that although women still predominate in the general population, the ratio of women to men with panic disorder and agoraphobia (about 2:1) is not as extreme as in clinical samples (Kessler et al., 2006).The mass of research on interpersonal aspects of agoraphobia is substantially greater and older than that for the other anxiety disorders. No doubt this is because the role of the phobic companion in agoraphobia is so striking that the interpersonal context of the disorder could not be ignored. Marks (1970) estimated that 95% of people with agoraphobia are able to venture further into phobic situations or to enter phobic situations with less anxiety if accompanied by a trusted other. In laboratory research, Carter, Hollon, Carson, and Shelton (1995) demonst...