One of the most striking characteristics of patients in a mental hospital diagnosed as suffering from schizophrenia, or dementia præcox, is their dissimilarity. It is easy to pick out cases in which the onset, course, symptomatology and outcome of the psychosis are different. There is thus a tendency to regard the schizophrenic group as possibly containing many different clinical entities. One of the current major problems of psychiatry is to clarify what constitutes schizophrenia and to subdivide the clinical material further in a way which will prove useful for study.