ABSTRACT A decrease in central serotonin metabolism has been found in suicidal patients. In schizophrenic patients suicidality is predominantly observed as a transient phenomenon being most pronounced during an acute psychotic episode. We investigated blood serotonin levels as a paradigm for serotonin metabolism in suicidal schizophrenic women who were psychotic and compared their data with those of nonsuicidal psychotic schizophrenic women and healthy controls. Blood serotonin was lower in suicidal female schizophrenic patients (0.44 ± 0.05 μmol/1, n= 17) than in nonsuicidal female schizophrenic patients (0.94 ± 0.07 μmol/1, n= 17; P < 0.001) or in healthy women (0.90 ± 0.02 μmol/1, <n= 26; P <0.001). These findings support the hypothesis that decreased serotonin metabolism may be associated with suicidal behavior in schizophrenic women.