The accumulating research evidence for the psychobiological reconceptualization of suicidal behaviour is briefly reviewed, particularly regarding the serotonin hypothesis of suicide risk. The first suggestion of a link between suicide and serotonin came with the biochemical results from postmortem brain studies of suicide victims. Currently available research data suggest decreased brain stem levels of serotonin and 5-HIAA, altered distribution of presynaptic binding of the ligand 3H-imipramine to serotonin neurons and a region-specific increase in the number of postsynaptic 5HT2 receptors in the prefrontal cortex in suicide victims. Early CSF studies have indicated decreased CSF 5-HIAA in patients recently attempting suicide and follow-up studies of large samples of mood-disorder patients confirm the original hypothesis that low CSF 5-HIAA predicts suicide risk after attempted suicide. However, the clinical utility of these compelling biological correlates of suicide in the management of suicide risk in psychiatric patients will depend on the results of psychopharmacological treatment research targeting suicidal behaviour.