Résumé : The preliminary double-blind cross-over study does not indicate that ceruletide exerts antipsychotic action on schizophrenic patients free from neuroleptics. Because schizophrenia is an heterogenous disorder, a differential response to ceruletide in certain subtypes (particularly in acute cases) cannot be excluded at the present stage. A reduction of CCK levels is reported in the CSF of parkinsonian and schizophrenic patients free of neuroleptics. A double-blind cross-over study does not show that ceruletide has antipsychotic properties in neuroleptic-free patients suffering from schizophrenia.