Desensitization of psychological and physiological complex structures may be the most important element of flooding treatment. The implosive sessions are assumed to represent a supramaximal stimulation of pathologically excited and inert complex structures resulting in protective inhibition, irradiation of excitation, reduction of the excitation and inertness, and a decrease of the overshooting autonomic reactivity of the complex structures, leading to reduction of anxiety, aggression, and other pathologically increased feelings. Advantages such as stronger and improved flooding can be achieved by a flooding in hypnosis. The therapeutic indications go beyond the usual treatment of phobic states. In order to establish the psychological and physiological mechanisms in implosion there is a need for psychophysiological investigations. However, much is unknown about mechanisms. Controlled comparisons with other treatments give limited answers. Perhaps an international case history bank might establish which clinical conditions might benefit by technical modifications of flooding.