It is well known that obsessive-compulsive symptoms may occur in the prodromal phase or in the course of schizophrenia, and that schizophrenic symptoms may supervene in a long-standing obsessional neurosis. Stengel (1945) has reviewed much of the earlier literature concerning the relationships between obsessional neurosis and schizophrenia. The question whether obsessional neurosis could develop into schizophrenia has often been discussed. Pilcz (1922), Legewie (1923) and Schneider (1925) distinguished between genuine obsessions which were symptoms of an obsessional neurosis, and symptomatic obsessional ideas which could occur in various conditions. These authors, as well as Stekel (1950), doubted whether a genuine obsessional neurosis could develop into schizophrenia. Bleuler (1911) thought that some patients suffering with chronic obsessional symptoms were in fact schizophrenic, especially where a schizophrenic psychosis had been observed in the family. Mayer-Gross (1932) expressed the view that cases of obsessive-compulsive neurosis existing over decades without change and presenting marked autism were often schizophrenics. Together with Bleuler, Mayer-Gross suspected that many of Janet's “psychasthenic” patients had been schizophrenic. Janet (1903) had observed 3,000 cases of psychasthenia, of which 12 developed into psychosis, and two into hebephrenia, but Janet's psychasthenia probably included cases other than obsessional neurosis. There is a well-known case which showed how in the course of a long-standing obsessional neurosis, paranoid schizophrenic symptoms may make their appearance. This is the patient described by Freud (1918) in “The History of an Infantile Neurosis”, who, many years after he had been treated by Freud for obsessional symptoms, was treated for a paranoid state by Ruth Mack Brunswick (1928).