The fog – invisibility as protection and defence organization The paper examines the complex functions of a traumatic defence organization which the patient herself described as »fog«. During day hospital treatment four different phases could be discerned: (1) the disruption of memory and linking, (2) the role of intrapsychic derealisation, (3) the emergence of perverse links and, finally (4) the invasion of the »fog« into the countertransference. To conclude, the clinical material is discussed in the context of the role of defence mechanisms in traumatic experiences and the building of pathological organizations of the personality.