A classification of chronic psychoses including nonparanoid schizophrenia, paranoid schizophrenia, paranoid state and paranoia (delusional disorder) is presented. This classification is dependent on a systematic increase in number of symptoms with each group. In particular, delusional disorder is examined with regard to family history. It is clear from the data which are presented that delusional disorder is more likely to be associated with a family history of such traits as suspiciousness, jealousy, secretiveness, and the presence of paranoid behavior or delusions. There is evidence that such familial traits are not seen in schizophrenia, only in delusional disorder.