Letter to the editor. Research shows low cerebrospinal fluid values of 5-HIAA related to depression & very low levels related to violent attempted suicide. The study reported here, a comparison of post-probenicid CSF 5-HIAA levels in non-depressed schizophrenics without & with suicidal histories (violent & nonviolent) & non-psychiatric controls, supports the hypothesis that low CSTF 5-HIAA relates to suicidal behavior irrespective of diagnostic category. (GW)