A series of manifest dreams shows clearly that each patient has characteristic methods of dealing with id impulses. In the attempt to develop 'an alphabet of defence mechanisms, a catalogue of elementary responses' (Waelder), the authors have devised a complex rating system for ego defences based on the degree of awareness of impulses. This system differentiated successfully between the manifest content of the dreams of psychotics, criminals, and normal subjects, when experienced analysts had not been able to do so by inspection.