The distinction between schizophrenia and chronic delusion syndromes (such as paraphrenia, late-paraphrenia and "Psychose Hallucinatoire Chronique") is currently used in France, although there is no international criteria (ICD 10 or DSM IV) for chronic delusion syndromes. It is thus worth analysing the literature in order to compare the differences between late-onset schizophrenia and "Psychose Hallucinatoire Chronique", and the similarities between young-onset schizophrenia and chronic delusion syndromes. Clinical investigations clearly differentiate "Psychose Hallucinatoire Chronique" and late-onset-schizophrenia from young-onset schizophrenia because they have more delusion and hallucinatory symptoms, less negative symptoms, better evolution, and better sensitivity to antipsychotic drugs. Epidemiological data show that "Psychose Hallucinatoire Chronique" and late-onset schizophrenia have both a different sex-ratio (around 7 women for 1 man) than young-onset schizophrenia (nearly 1 woman for 1 man), and that in "Psychose Hallucinatoire Chronique" and in late-onset schizophrenia, social withdrawal is frequently observed before onset of the disorder. Lastly, putative risk factors may be shared by "Psychose Hallucinatoire Chronique" and late-onset schizophrenia, and may isolate them from young-onset schizophrenia, for example regarding the oestradiol hypothesis (oestradiol enhance dopamine efficacy and delay the onset of delusion disorders), the impact of sensory handicaps (which may be clinically and experimentally associated with hallucinations), or the role of genetic and familial factors (with a familial concentration intermediate between the familial concentration of schizophrenia of schizophrenic proband, and the familial concentration of schizophrenia of control probands). In accordance with this review of the literature, the authors conclude that the absence of specific criteria for late-onset schizophrenia and/or "Psychose Hallucinatoire Chronique" In international diagnostic manual risk to counter the facility to detect specific risk factors involved in the pathogenesis of schizophrenia.