Prince has written a detailed study of an experience with two patients possessed (or obsessed) by the spirit of a person, once known, who had died. The therapist exhorted the dead person in the presence of the patient and had the patient do automatic writing. Contact with the patient was over a period of one or two years and there was no relapse back into a feeling of being possessed. Other patients treated by the same technique did not respond with relief. The difference was that they felt possessed either by unfamiliar persons or by living persons and so the author calls their problem delusionary. No list of references is included.