The monoamine metabolites 5-hydroxindoleacetic acid (5-HIAA), homovanillic acid (HVA) and 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) were measured in the lumbar cerebrospinal fluid (CSF) of 27 chronic schizophrenic patients who at some time had attempted suicide, and were compared with values from 27 chronic schizophrenic patients without a history of attempted suicide. There were no significant differences between either the violent or non-violent attempters and those without a history of attempted suicide in the mean lumbar CSF concentrations of the serotonin metabolite 5-HIAA, the dopamine metabolite HVA, or the norepinephrine metabolite MHPG. Significantly more of the suicide attempters had a previous major depressive episode, had received a course of ECT, and had significantly more psychiatric admissions than those who had never attempted suicide.