The purpose of this study was to investigate, in schizophrenic patients, the relationship between suicidal behaviour & prolactin (PRL) response to D-fenfluramine (D-FEN). A D-FEN test was performed in 18 healthy controls & 33 drug-free DSM-IV schizophrenic patients (12 with a history of suicide attempts, 21 without it). Schizophrenic patients with a history of suicide attempts showed a lower PRL response to D-FEN (DeltaPRL) compared to schizophrenic patients without such history. These results suggest that PRL response to D-FEN is a marker of suicidality also in schizophrenia, supporting the hypothesis that a dysfunction in serotonergic function is associated with suicidal behaviour regardless of the psychiatric diagnosis. (75 refs)