The authors report on several cases which confirm the opinion of Grinker and MacLean that 'convulsive shocks produce physiological disturbances in the brain which affect the dynamic relationship between the inhibiting, repressing functions and the inhibited repressed aggressive drives resulting in a freer expression of these affects more directly in dream, fantasy, verbal or motor activity'. If possible psychotherapy should handle these newly mobilized aggressive tendencies. The liberation of the aggressive drives may be favorable even if not accompanied by any conscious understanding of the process. The authors warn of the possibility of a depression turning into a manic attack when treated by shock therapy.