The authors present the proposed DSM-III classification of the traditional hysterical disorders, i.e., disorders that suggest physical illness but in which psychological factors are judged to be of importance. The use of the DSM-III inclusion and exclusion criteria—physical mechanism explains the symptom, symptoms are linked to psychological factors, symptom initiation is under voluntary control, and there is an obvious recognizable environmental goal—are discussed in the differential diagnosis of somatoform disorder, factitious disorder, malingering, psychological factors affecting physical condition, and undiagnosed physical illness.