An attempt has been made to understand what happens in the course of shock treatment. It is felt that shock treatment is an experience, producing alterations in the somato-psychic homeostasis leading to a disruption of the hitherto existing mechanisms which tend to maintain this homeostasis. In its attempts to re-establish the hitherto existing equilibrium, the ego may be successful, partially successful or unsuccessful, thus producing various clinical syndromes. The ego may defensively regress to more primitive narcissistic levels. This step brings with it more archaic defensive mechanisms in the attempt of the ego to hold on to some degree of reality. This may be only temporary and after a while it is possible that the ego may muster its forces and re-establish its previous or perhaps even a better adaptive defensive apparatus. All of these maneuvers produce varying kinds of clinical reactions some of which are described.