Previous investigations have suggested that desensitization is the treatment of choice for simple phobic disorders, but is less effective with agoraphobia, particularly when the phobias are accompanied by much generalized anxiety (Gelder and Marks, 1966). Even the milder agoraphobias usually respond incompletely despite prolonged treatment. An alternative treatment that offers more rapid or effective results, particularly with agoraphobia, would therefore be of value. The technique of flooding or implosion has recently been the subject of a number of studies, and some, but not all, have shown evidence of considerable therapeutic power. The method is also of some theoretical interest since it breaks the rules which are thought to be important in desensitization. Thus, according to early proponents (Stampfl and Levis, 1967) success depends on exposing patients to fantasy material of an extremely intense and anxiety-provoking nature, so that extinction to cues associated with the original traumatic situation may take place. From this theoretical viewpoint desensitization can be only partially successful, since these traumatic origins are neither sought for nor presented to the patient. Even if the necessity of dealing with original anxiety-provoking cues is not accepted, the use of material which evokes maximal anxiety for prolonged periods is contrary to the counter-conditioning theory of desensitization (Wolpe, 1958). Indeed, this theory predicts that flooding would rarely be successful and might make the phobia worse because uncontrolled increases in anxiety may cause reconditioning.